Configuration of a first message for a two-step random access channel procedure

ABSTRACT

A user equipment (UE) may be configured to receive configuration information from a base station, and the configuration information may indicate at least two different random access channel (RACH) request configuration parameters that each is associated with a respective radio resource control (RRC) state. The UE may be further configured to generate a first message associated with a two-step RACH procedure including a preamble and a payload, the payload including data on an uplink data channel and at least one reference signal. The UE may be further configured to transmit the first message to the base station using at least one of the at least two different RACH request configuration parameters that corresponds to an RRC state of the UE. The preamble may be transmitted on a first set of resources associated with a RACH occasion, and the payload may be transmitted on a second set of resources.

CROSS REFERENCE TO RELATED APPLICATION(S)

This application is a Continuation of U.S. patent application Ser. No.16/743,673, entitled “CONFIGURATION OF A FIRST MESSAGE FOR A TWO-STEPRANDOM ACCESS CHANNEL PROCEDURE” and filed on Jan. 15, 2020, whichclaims the benefit of U.S. Provisional Application Ser. No. 62/795,510,entitled “CONFIGURATION OF A FIRST MESSAGE FOR A TWO-STEP RANDOM ACCESSCHANNEL PROCEDURE” and filed on Jan. 22, 2019, which are expresslyincorporated by reference herein in their entirety.

BACKGROUND Technical Field

The present disclosure relates generally to communications systems, andmore particularly, to a user equipment and base station configured toperform a two-step random access channel procedure.

Introduction

Wireless communication systems are widely deployed to provide varioustelecommunication services such as telephony, video, data, messaging,and broadcasts. Typical wireless communication systems may employmultiple-access technologies capable of supporting communication withmultiple users by sharing available system resources. Examples of suchmultiple-access technologies include code division multiple access(CDMA) systems, time division multiple access (TDMA) systems, frequencydivision multiple access (FDMA) systems, orthogonal frequency divisionmultiple access (OFDMA) systems, single-carrier frequency divisionmultiple access (SC-FDMA) systems, and time division synchronous codedivision multiple access (TD-SCDMA) systems.

These multiple access technologies have been adopted in varioustelecommunication standards to provide a common protocol that enablesdifferent wireless devices to communicate on a municipal, national,regional, and even global level. An example telecommunication standardis 5G New Radio (NR). 5G NR is part of a continuous mobile broadbandevolution promulgated by Third Generation Partnership Project (3GPP) tomeet new requirements associated with latency, reliability, security,scalability (e.g., with Internet of Things (IoT)), and otherrequirements. 5G NR includes services associated with enhanced mobilebroadband (eMBB), massive machine type communications (mMTC), and ultrareliable low latency communications (URLLC). Some aspects of 5G NR maybe based on the 4G Long Term Evolution (LTE) standard. There exists aneed for further improvements in 5G NR technology. These improvementsmay also be applicable to other multi-access technologies and thetelecommunication standards that employ these technologies.

SUMMARY

The following presents a simplified summary of one or more aspects inorder to provide a basic understanding of such aspects. This summary isnot an extensive overview of all contemplated aspects, and is intendedto neither identify key or critical elements of all aspects nordelineate the scope of any or all aspects. Its sole purpose is topresent some concepts of one or more aspects in a simplified form as aprelude to the more detailed description that is presented later.

In many radio access networks (RANs), user equipment (UE) obtaininformation that facilitates communication with base stations duringinitial access, handover between base stations, connectionreestablishment, and so forth. For example, a UE may acquire uplinktiming synchronization with a base station and/or an uplink grant for atransmission to the base station from such information. This informationmay be determined by the base station and provided to the UE through arandom access channel (RACH) procedure.

A RACH procedure typically involves the exchange of messages between aUE and a base station, such as three messages for a contention-free RACHprocedure or four messages for a contention-based RACH procedure. The UEmay refrain from including data in messages transmitted to the basestation for such RACH procedures, e.g., because the UE has not yetacquired a timing advance.

Such contention-free and contention-based RACH procedures may incuroverhead with respect to over-the-air signaling, timing, processing andpower consumption, and so forth. The present disclosure, however,provides for a two-step RACH procedure, for example, for application in5G New Radio (NR) RANs. Such a two-step RACH procedure may address someoverhead issues associated with four-step contention-based and/orthree-step contention-free RACH procedures. For example, a UE withoutvalid timing advance may initiate the two-step RACH procedure with amessage that includes an uplink data channel. Furthermore, the two-stepRACH procedure described in the present disclosure may be applicable tomost or all cell types and sizes operated by base stations, as well asapplicable to most or all radio resource control (RRC) states in whichUEs may operate.

Commensurate with the fewer number of messages exchanged during RACHprocedures, a greater amount of information may be included in and/or agreater amount of resources may be allocated for one of both of a firstmessage (referred to as “msgA”) transmitted by a UE to initiate atwo-step RACH procedure and/or a second message (referred to as “msgB”)transmitted by a base station to complete the two-step RACH procedure.Therefore, a need exists for techniques and approaches to configuring aUE and a base station for a two-step RACH procedure, as described in thepresent disclosure.

In one aspect of the disclosure, a method, a computer-readable medium,and an apparatus are provided. The apparatus may be a UE configured toreceive configuration information from a base station, the configurationinformation indicating at least two different RACH request configurationparameters that each is associated with a respective radio resourcecontrol (RRC) state; generate a first message associated with a two-stepRACH procedure including a preamble and a payload, the payload includingdata on an uplink data channel and at least one reference signal; andtransmit the first message to the base station using at least one of theat least two different RACH request configuration parameters thatcorresponds to an RRC state of the UE, the preamble being transmitted ona first set of resources associated with a RACH occasion and the payloadbeing transmitted on a second set of resources.

In one aspect, the uplink data channel includes a physical uplink sharedchannel (PUSCH), and the at least one reference signal includes ademodulation reference signal (DMRS). In one aspect, the configurationinformation is included in at least one of a system information block(SIB) or a RRC message from the base station.

In one aspect, the apparatus may be further configured to determine atleast one power control scheme for transmission of the first messagebased on a modulation and coding scheme (MCS) and bandwidth configuredfor the payload, wherein the at least one power control scheme isindicated in the at least two different RACH request configurationparameters. In one aspect, the preamble and the payload are transmittedusing different power control schemes indicated by the at least one ofthe at least two different RACH request configuration parameters.

In one aspect, the first message includes a time gap between thepreamble and the payload, and the time gap includes a configurablenumber of slots or symbols between the preamble and the payload. In oneaspect, the preamble indicates at least one of a size of the payload ora MCS configured for the payload. In one aspect, the configurationinformation indicates at least one configuration in a time domain, afrequency domain, or a spatial domain for the first set of resourcesassociated with the RACH occasion.

In one aspect, the configuration information indicates at least one of:a physical RACH (PRACH) configuration index associated with at least oneRACH occasion configuration in the time domain, a number of RACHoccasions available for the RACH procedure associated with the at leastone configuration in the frequency domain, a starting frequency resourceassociated with the RACH occasions, a number of preamble sequences persynchronization signal (SS)/physical broadcast channel (PBCH) block, ora number of SS/PBCH blocks associated with each of the RACH occasions.In one aspect, the RRC state of the UE is associated with at least oneof a size of the payload or a MCS configured for the payload.

In one aspect, at least one of a sequence length associated with thepreamble or a subcarrier spacing associated with the transmission of thefirst message is based on at least one of a type of a cell operated bythe base station or the RRC state of the UE. In one aspect, the preambleoccupies a different bandwidth portion than the payload,

the preamble is transmitted with a different target power or a differentpower ramping step size than the payload, the preamble is transmittedvia a different beam pair than the payload, or the preamble istransmitted with a different subcarrier spacing than the payload.

In one aspect, the apparatus may be is further configured to receive asecond message associated with the two-step RACH procedure from the basestation in response to the first message, wherein the second messageincludes control information on a downlink control channel and data on adownlink data channel. In one aspect, the first message includes a msgAinitiating the two-step RACH procedure and the second message includes amsgB enabling completion of the two-step RACH procedure.

In another aspect of the disclosure, another method, anothercomputer-readable medium, and another apparatus are provided. The otherapparatus may be a base station configured to transmit configurationinformation indicating at least two different RACH request configurationparameters that each is associated with a respective RRC state; receivea first message associated with the RACH procedure from a UE based onthe configuration information, a preamble of the first message beingreceived on a first set of resources associated with a RACH occasion anda payload of the first message being received on a second set ofresources; and transmit a second message associated with the RACHprocedure to the UE in response to the first message, the second messageincluding control information on a downlink control channel and data ona downlink data channel.

In one aspect, the downlink control channel includes a physical downlinkcontrol channel (PDCCH) and the downlink data channel includes aphysical downlink shared channel (PDSCH). In one aspect, theconfiguration information indicating the RACH request configurationparameters is transmitted in a RRC message to the UE or broadcast in aSIB. In one aspect, the first message includes a time gap between thepreamble and the payload, and the time gap includes a configurablenumber of slots or symbols between the preamble and the payload.

In one aspect, the other apparatus may be further configured todetermine at least one of a size of the payload or a MCS configured forthe payload based on the preamble of the first message. In one aspect,the configuration information indicates at least one configuration in atime domain, a frequency domain, or a spatial domain for the first setof resources associated with the RACH occasion.

In one aspect, the configuration information indicates at least one of:a configuration index associated with the configuration in the timedomain, a number of RACH occasions available for the RACH procedureassociated with the configuration in the frequency domain, a startingfrequency resource associated with the RACH occasions, a number ofpreamble sequences per SS/PBCH block, or a number of SS/PBCH blocksassociated with each of the RACH occasions. In one aspect, at least oneof a size of the payload or a MCS configured for the payload is based onan RRC state of the UE.

In one aspect, at least one of a sequence length associated with thepreamble or a subcarrier spacing associated with the receiving the firstmessage is based on at least one of a type of a cell operated by thebase station or an RRC state of the UE. In one aspect, the preambleoccupies a different bandwidth portion than the payload, the preamble istransmitted with a different target power or a different power rampingstep size than the payload, the preamble is received via a differentbeam pair than the payload, or the preamble is received with a differentsubcarrier spacing than the payload. In one aspect, the RACH procedureincludes a two-step RACH procedure, and wherein the first messageincludes a msgA initiating the two-step RACH procedure and the secondmessage includes a msgB enabling completion of the two-step RACHprocedure.

To the accomplishment of the foregoing and related ends, the one or moreaspects comprise the features hereinafter fully described andparticularly pointed out in the claims. The following description andthe annexed drawings set forth in detail certain illustrative featuresof the one or more aspects. These features are indicative, however, ofbut a few of the various ways in which the principles of various aspectsmay be employed, and this description is intended to include all suchaspects and their equivalents.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating an example of a wireless communicationssystem and an access network.

FIGS. 2A, 2B, 2C, and 2D are diagrams illustrating examples of a first5G/NR frame, DL channels within a 5G/NR subframe, a second 5G/NR frame,and UL channels within a 5G/NR subframe, respectively.

FIG. 3 is a diagram illustrating an example of a base station and userequipment (UE) in an access network.

FIG. 4 is a call flow diagram of wireless communications system.

FIG. 5 is a block diagram of a transmit chain for a message of a randomaccess channel procedure.

FIG. 6 is a block diagram of resource allocations and sequenceconfigurations for preambles of random access channel procedures.

FIG. 7 is a block diagram of composite preambles for messages of randomaccess channel procedures.

FIG. 8 is a flowchart of a method of wireless communication by a UE.

FIG. 9 is a flowchart of a method of wireless communication by a UE.

FIG. 10 is a flowchart of a method of wireless communication by a UE.

FIG. 11 is a flowchart of a method of wireless communication by a basestation.

FIG. 12 is a conceptual data flow diagram illustrating the data flowbetween different means/components in an example apparatus.

FIG. 13 is a diagram illustrating an example of a hardwareimplementation for an apparatus employing a processing system.

FIG. 14 is a conceptual data flow diagram illustrating the data flowbetween different means/components in an example apparatus.

FIG. 15 is a diagram illustrating an example of a hardwareimplementation for an apparatus employing a processing system.

DETAILED DESCRIPTION

The detailed description set forth below in connection with the appendeddrawings is intended as a description of various configurations and isnot intended to represent the only configurations in which the conceptsdescribed herein may be practiced. The detailed description includesspecific details for the purpose of providing a thorough understandingof various concepts. However, it will be apparent to those skilled inthe art that these concepts may be practiced without these specificdetails. In some instances, well known structures and components areshown in block diagram form in order to avoid obscuring such concepts.

Several aspects of telecommunications systems will now be presented withreference to various apparatus and methods. These apparatus and methodswill be described in the following detailed description and illustratedin the accompanying drawings by various blocks, components, circuits,processes, algorithms, etc. (collectively referred to as “elements”).These elements may be implemented using electronic hardware, computersoftware, or any combination thereof. Whether such elements areimplemented as hardware or software depends upon the particularapplication and design constraints imposed on the overall system.

By way of example, an element, or any portion of an element, or anycombination of elements may be implemented as a “processing system” thatincludes one or more processors. Examples of processors includemicroprocessors, microcontrollers, graphics processing units (GPUs),central processing units (CPUs), application processors, digital signalprocessors (DSPs), reduced instruction set computing (RISC) processors,systems on a chip (SoC), baseband processors, field programmable gatearrays (FPGAs), programmable logic devices (PLDs), state machines, gatedlogic, discrete hardware circuits, and other suitable hardwareconfigured to perform the various functionality described throughoutthis disclosure. One or more processors in the processing system mayexecute software. Software shall be construed broadly to meaninstructions, instruction sets, code, code segments, program code,programs, subprograms, software components, applications, softwareapplications, software packages, routines, subroutines, objects,executables, threads of execution, procedures, functions, etc., whetherreferred to as software, firmware, middleware, microcode, hardwaredescription language, or otherwise.

Accordingly, in one or more example aspects, the functions described maybe implemented in hardware, software, or any combination thereof. Ifimplemented in software, the functions may be stored on or encoded asone or more instructions or code on a computer-readable medium.Computer-readable media includes computer storage media. Storage mediamay be any available media that can be accessed by a computer. By way ofexample, and not limitation, such computer-readable media can comprise arandom-access memory (RAM), a read-only memory (ROM), an electricallyerasable programmable ROM (EEPROM), optical disk storage, magnetic diskstorage, other magnetic storage devices, combinations of theaforementioned types of computer-readable media, or any other mediumthat can be used to store computer executable code in the form ofinstructions or data structures that can be accessed by a computer.

FIG. 1 is a diagram illustrating an example of a wireless communicationssystem and an access network 100. The wireless communications system(also referred to as a wireless wide area network (WWAN)) includes basestations 102, UEs 104, an Evolved Packet Core (EPC) 160, and anothercore network 190 (e.g., a 5G Core (5GC)). The base stations 102 mayinclude macrocells (high power cellular base station) and/or small cells(low power cellular base station). The macrocells include base stations.The small cells include femtocells, picocells, and microcells.

The base stations 102 configured for 4G Long Term Evolution (LTE)(collectively referred to as Evolved Universal Mobile TelecommunicationsSystem (UMTS) Terrestrial Radio Access Network (E-UTRAN)) may interfacewith the EPC 160 through backhaul links 132 (e.g., S1 interface). Thebase stations 102 configured for 5G New Radio (NR) (collectivelyreferred to as Next Generation RAN (NG-RAN)) may interface with corenetwork 190 through backhaul links 184. In addition to other functions,the base stations 102 may perform one or more of the followingfunctions: transfer of user data, radio channel ciphering anddeciphering, integrity protection, header compression, mobility controlfunctions (e.g., handover, dual connectivity), inter-cell interferencecoordination, connection setup and release, load balancing, distributionfor non-access stratum (NAS) messages, NAS node selection,synchronization, radio access network (RAN) sharing, multimediabroadcast multicast service (MBMS), subscriber and equipment trace, RANinformation management (RIM), paging, positioning, and delivery ofwarning messages. The base stations 102 may communicate directly orindirectly (e.g., through the EPC 160 or core network 190) with eachother over backhaul links 134 (e.g., X2 interface). The backhaul links134 may be wired or wireless.

The base stations 102 may wirelessly communicate with the UEs 104. Eachof the base stations 102 may provide communication coverage for arespective geographic coverage area 110. There may be overlappinggeographic coverage areas 110. For example, the small cell 102′ may havea coverage area 110′ that overlaps the coverage area 110 of one or moremacro base stations 102. A network that includes both small cell andmacrocells may be known as a heterogeneous network. A heterogeneousnetwork may also include Home Evolved Node Bs (eNBs) (HeNBs), which mayprovide service to a restricted group known as a closed subscriber group(CSG). The communication links 120 between the base stations 102 and theUEs 104 may include uplink (UL) (also referred to as reverse link)transmissions from a UE 104 to a base station 102 and/or downlink (DL)(also referred to as forward link) transmissions from a base station 102to a UE 104. The communication links 120 may use multiple-input andmultiple-output (MIMO) antenna technology, including spatialmultiplexing, beamforming, and/or transmit diversity. The communicationlinks may be through one or more carriers. The base stations 102/UEs 104may use spectrum up to Y MHz (e.g., 5, 10, 15, 20, 100, 400, etc. MHz)bandwidth per carrier allocated in a carrier aggregation of up to atotal of Yx MHz (x component carriers) used for transmission in eachdirection. The carriers may or may not be adjacent to each other.Allocation of carriers may be asymmetric with respect to DL and UL(e.g., more or fewer carriers may be allocated for DL than for UL). Thecomponent carriers may include a primary component carrier and one ormore secondary component carriers. A primary component carrier may bereferred to as a primary cell (PCell) and a secondary component carriermay be referred to as a secondary cell (SCell).

Certain UEs 104 may communicate with each other using device-to-device(D2D) communication link 158. The D2D communication link 158 may use theDL/UL WWAN spectrum. The D2D communication link 158 may use one or moresidelink channels, such as a physical sidelink broadcast channel(PSBCH), a physical sidelink discovery channel (PSDCH), a physicalsidelink shared channel (PSSCH), and a physical sidelink control channel(PSCCH). D2D communication may be through a variety of wireless D2Dcommunications systems, such as for example, FlashLinQ, WiMedia,Bluetooth, ZigBee, Wi-Fi based on the IEEE 802.11 standard, LTE, or NR.

The wireless communications system may further include a Wi-Fi accesspoint (AP) 150 in communication with Wi-Fi stations (STAs) 152 viacommunication links 154 in a 5 GHz unlicensed frequency spectrum. Whencommunicating in an unlicensed frequency spectrum, the STAs 152/AP 150may perform a clear channel assessment (CCA) prior to communicating inorder to determine whether the channel is available.

The small cell 102′ may operate in a licensed and/or an unlicensedfrequency spectrum. When operating in an unlicensed frequency spectrum,the small cell 102′ may employ NR and use the same 5 GHz unlicensedfrequency spectrum as used by the Wi-Fi AP 150. The small cell 102′,employing NR in an unlicensed frequency spectrum, may boost coverage toand/or increase capacity of the access network.

A base station 102, whether a small cell 102′ or a large cell (e.g.,macro base station), may include an eNB, gNodeB (gNB), or another typeof base station. Some base stations, such as gNB 180 may operate in atraditional sub 6 GHz spectrum, in millimeter wave (mmW) frequencies,and/or near mmW frequencies in communication with the UE 104. When thegNB 180 operates in mmW or near mmW frequencies, the gNB 180 may bereferred to as an mmW base station. Extremely high frequency (EHF) ispart of the RF in the electromagnetic spectrum. EHF has a range of 30GHz to 300 GHz and a wavelength between 1 millimeter and 10 millimeters.Radio waves in the band may be referred to as a millimeter wave. NearmmW may extend down to a frequency of 3 GHz with a wavelength of 100millimeters. The super high frequency (SHF) band extends between 3 GHzand 30 GHz, also referred to as centimeter wave. Communications usingthe mmW/near mmW radio frequency band (e.g., 3 GHz-300 GHz) hasextremely high path loss and a short range. The mmW base station 180 mayutilize beamforming 182 with the UE 104 to compensate for the extremelyhigh path loss and short range.

The base station 180 may transmit a beamformed signal to the UE 104 inone or more transmit directions 182′. The UE 104 may receive thebeamformed signal from the base station 180 in one or more receivedirections 182″. The UE 104 may also transmit a beamformed signal to thebase station 180 in one or more transmit directions. The base station180 may receive the beamformed signal from the UE 104 in one or morereceive directions. The base station 180/UE 104 may perform beamtraining to determine the best receive and transmit directions for eachof the base station 180/UE 104. The transmit and receive directions forthe base station 180 may or may not be the same. The transmit andreceive directions for the UE 104 may or may not be the same.

The EPC 160 may include a Mobility Management Entity (MME) 162, otherMMES 164, a Serving Gateway 166, a Multimedia Broadcast MulticastService (MBMS) Gateway 168, a Broadcast Multicast Service Center (BM-SC)170, and a Packet Data Network (PDN) Gateway 172. The MME 162 may be incommunication with a Home Subscriber Server (HSS) 174. The MME 162 isthe control node that processes the signaling between the UEs 104 andthe EPC 160. Generally, the MME 162 provides bearer and connectionmanagement. All user Internet protocol (IP) packets are transferredthrough the Serving Gateway 166, which itself is connected to the PDNGateway 172. The PDN Gateway 172 provides UE IP address allocation aswell as other functions. The PDN Gateway 172 and the BM-SC 170 areconnected to the IP Services 176. The IP Services 176 may include theInternet, an intranet, an IP Multimedia Subsystem (IMS), a PS StreamingService, and/or other IP services. The BM-SC 170 may provide functionsfor MBMS user service provisioning and delivery. The BM-SC 170 may serveas an entry point for content provider MBMS transmission, may be used toauthorize and initiate MBMS Bearer Services within a public land mobilenetwork (PLMN), and may be used to schedule MBMS transmissions. The MBMSGateway 168 may be used to distribute MBMS traffic to the base stations102 belonging to a Multicast Broadcast Single Frequency Network (MBSFN)area broadcasting a particular service, and may be responsible forsession management (start/stop) and for collecting eMBMS relatedcharging information.

The core network 190 may include a Access and Mobility ManagementFunction (AMF) 192, other AMFs 193, a Session Management Function (SMF)194, and a User Plane Function (UPF) 195. The AMF 192 may be incommunication with a Unified Data Management (UDM) 196. The AMF 192 isthe control node that processes the signaling between the UEs 104 andthe core network 190. Generally, the AMF 192 provides QoS flow andsession management. All user Internet protocol (IP) packets aretransferred through the UPF 195. The UPF 195 provides UE IP addressallocation as well as other functions. The UPF 195 is connected to theIP Services 197. The IP Services 197 may include the Internet, anintranet, an IP Multimedia Subsystem (IMS), a PS Streaming Service,and/or other IP services.

The base station may also be referred to as a gNB, Node B, evolved NodeB (eNB), an access point, a base transceiver station, a radio basestation, a radio transceiver, a transceiver function, a basic serviceset (B SS), an extended service set (ESS), a transmit reception point(TRP), or some other suitable terminology. The base station 102 providesan access point to the EPC 160 or core network 190 for a UE 104.Examples of UEs 104 include a cellular phone, a smart phone, a sessioninitiation protocol (SIP) phone, a laptop, a personal digital assistant(PDA), a satellite radio, a global positioning system, a multimediadevice, a video device, a digital audio player (e.g., MP3 player), acamera, a game console, a tablet, a smart device, a wearable device, avehicle, an electric meter, a gas pump, a large or small kitchenappliance, a healthcare device, an implant, a sensor/actuator, adisplay, or any other similar functioning device. Some of the UEs 104may be referred to as IoT devices (e.g., parking meter, gas pump,toaster, vehicles, heart monitor, etc.). The UE 104 may also be referredto as a station, a mobile station, a subscriber station, a mobile unit,a subscriber unit, a wireless unit, a remote unit, a mobile device, awireless device, a wireless communications device, a remote device, amobile subscriber station, an access terminal, a mobile terminal, awireless terminal, a remote terminal, a handset, a user agent, a mobileclient, a client, or some other suitable terminology.

Although the present disclosure may focus on 5G NR, the concepts andvarious aspects described herein may be applicable to other similarareas, such as LTE, LTE-Advanced (LTE-A), Code Division Multiple Access(CDMA), Global System for Mobile communications (GSM), or otherwireless/radio access technologies.

Referring again to FIG. 1, in certain aspects, the base station 102/180may transmit configuration information associated with a random accesschannel (RACK) procedure, which may be received by the UE 104 in thecoverage area 110 of the base station 102/180. The configurationinformation may indicate information associated with a two-step RACHprocedure, such as at least two different RACH request configurationparameters with which the UE 104 may be configured. For example, theconfiguration information may indicate at least two different preamblegroups, at least two different payload sizes, at least two differentMCSs, at least two different time and frequency resource allocations,and/or or at least two different power control schemes. Each of the atleast two different RACH request configuration parameters may correspondto a respective radio resource control (RRC) state, such as RRC Idle,RRC Inactive, or RRC Connected.

After reception of the configuration information, the UE 104 maygenerate a first message associated with the two-step RACH procedure.The first message may include a preamble and a payload, which mayfurther include data on an uplink data channel and at least onereference signal. The UE 104 may transmit the first message (alsoreferred to as a “msgA”) to the base station 102/180 using at least oneof the at least two different RACH request configuration parameters(configured by the base station 102/180) that corresponds to an RRCstate of the UE 104 in order to initiate the two-step RACH procedure(198). In some aspects, the UE 104 may be configured to transmit thepreamble and the payload with different ones of the at least two powercontrol schemes.

The base station 102/180 may receive the first message and, in responseto the first message, may generate a second message (also referred to asa “msgB”). The second message may include control information on adownlink control channel and data on a downlink data channel. The basestation 102/180 may transmit the second message to the UE 104 in orderto complete the two-step RACH procedure (198).

The present disclosure may describe some additional aspects associatedwith the two-step RACH procedure (198).

FIG. 2A is a diagram 200 illustrating an example of a first subframewithin a 5G/NR frame structure. FIG. 2B is a diagram 230 illustrating anexample of DL channels within a 5G/NR subframe. FIG. 2C is a diagram 250illustrating an example of a second subframe within a 5G/NR framestructure. FIG. 2D is a diagram 280 illustrating an example of ULchannels within a 5G/NR subframe. The 5G/NR frame structure may be FDDin which for a particular set of subcarriers (carrier system bandwidth),subframes within the set of subcarriers are dedicated for either DL orUL, or may be TDD in which for a particular set of subcarriers (carriersystem bandwidth), subframes within the set of subcarriers are dedicatedfor both DL and UL. In the examples provided by FIGS. 2A, 2C, the 5G/NRframe structure is assumed to be TDD, with subframe 4 being configuredwith slot format 28 (with mostly DL), where D is DL, U is UL, and X isflexible for use between DL/UL, and subframe 3 being configured withslot format 34 (with mostly UL). While subframes 3, 4 are shown withslot formats 34, 28, respectively, any particular subframe may beconfigured with any of the various available slot formats 0-61. Slotformats 0, 1 are all DL, UL, respectively. Other slot formats 2-61include a mix of DL, UL, and flexible symbols. UEs are configured withthe slot format (dynamically through DL control information (DCI), orsemi-statically/statically through RRC signaling) through a receivedslot format indicator (SFI). Note that the description infra appliesalso to a 5G/NR frame structure that is TDD.

Other wireless communication technologies may have a different framestructure and/or different channels. A frame (10 ms) may be divided into10 equally sized subframes (1 ms). Each subframe may include one or moretime slots. Subframes may also include mini-slots, which may include 7,4, or 2 symbols. Each slot may include 7 or 14 symbols, depending on theslot configuration. For slot configuration 0, each slot may include 14symbols, and for slot configuration 1, each slot may include 7 symbols.The symbols on DL may be cyclic prefix (CP) OFDM (CP-OFDM) symbols. Thesymbols on UL may be CP-OFDM symbols (for high throughput scenarios) ordiscrete Fourier transform (DFT) spread OFDM (DFT-s-OFDM) symbols (alsoreferred to as single carrier frequency-division multiple access(SC-FDMA) symbols) (for power limited scenarios; limited to a singlestream transmission). The number of slots within a subframe is based onthe slot configuration and the numerology. For slot configuration 0,different numerologies μ 0 to 5 allow for 1, 2, 4, 8, 16, and 32 slots,respectively, per subframe. For slot configuration 1, differentnumerologies 0 to 2 allow for 2, 4, and 8 slots, respectively, persubframe. Accordingly, for slot configuration 0 and numerology μ, thereare 14 symbols/slot and 2^(μ) slots/subframe. The subcarrier spacing (SCS) and symbol length/duration are a function of the numerology. The SCSmay be equal to 2^(μ)*15 kHz, where μ is the numerology 0 to 5. As such,the numerology μ=0 has a SCS of 15 kHz and the numerology μ=5 has a SCSof 480 kHz. The symbol length/duration is inversely related to the SCS.FIGS. 2A-2D provide an example of slot configuration 0 with 14 symbolsper slot and numerology μ=0 with 1 slot per subframe. The SCS is 15 kHzand symbol duration is approximately 66.7 μs.

A resource grid may be used to represent the frame structure. Each timeslot includes a resource block (RB) (also referred to as physical RBs(PRBs)) that extends 12 consecutive subcarriers. The resource grid isdivided into multiple resource elements (REs). The number of bitscarried by each RE depends on the modulation scheme.

As illustrated in FIG. 2A, some of the REs carry reference (pilot)signals (RS) for the UE. The RS may include demodulation RS (DMRS)(indicated as R_(x) for one particular configuration, where 100× is theport number, but other DMRS configurations are possible) and channelstate information reference signals (CSI-RS) for channel estimation atthe UE. The RS may also include beam measurement RS (BRS), beamrefinement RS (BRRS), and phase tracking RS (PT-RS).

FIG. 2B illustrates an example of various DL channels within a subframeof a frame. The physical downlink control channel (PDCCH) carries DCIwithin one or more control channel elements (CCEs), each CCE includingnine RE groups (REGs), each REG including four consecutive REs in anOFDM symbol. A primary synchronization signal (PSS) may be within symbol2 of particular subframes of a frame. The PSS is used by a UE 104 todetermine subframe/symbol timing and a physical layer identity. Asecondary synchronization signal (SSS) may be within symbol 4 ofparticular subframes of a frame. The SSS is used by a UE to determine aphysical layer cell identity group number and radio frame timing. Basedon the physical layer identity and the physical layer cell identitygroup number, the UE can determine a physical cell identifier (PCI).Based on the PCI, the UE can determine the locations of theaforementioned DMRS. The physical broadcast channel (PBCH), whichcarries a master information block (MIB), may be logically grouped withthe PSS and SSS to form a synchronization signal (SS)/PBCH block. TheMIB provides a number of RBs in the system bandwidth and a system framenumber (SFN). The physical downlink shared channel (PDSCH) carries userdata, broadcast system information not transmitted through the PBCH suchas system information blocks (SIBs), and paging messages.

As illustrated in FIG. 2C, some of the REs carry DMRS (indicated as Rfor one particular configuration, but other DMRS configurations arepossible) for channel estimation at the base station. The UE maytransmit DMRS for the physical uplink control channel (PUCCH) and DMRSfor the physical uplink shared channel (PUSCH). The PUSCH DMRS may betransmitted in the first one or two symbols of the PUSCH. The PUCCH DMRSmay be transmitted in different configurations depending on whethershort or long PUCCHs are transmitted and depending on the particularPUCCH format used. Although not shown, the UE may transmit soundingreference signals (SRS). The SRS may be used by a base station forchannel quality estimation to enable frequency-dependent scheduling onthe UL.

FIG. 2D illustrates an example of various UL channels within a subframeof a frame. The PUCCH may be located as indicated in one configuration.The PUCCH carries uplink control information (UCI), such as schedulingrequests, a channel quality indicator (CQI), a precoding matrixindicator (PMI), a rank indicator (RI), and HARQ ACK/NACK feedback. ThePUSCH carries data, and may additionally be used to carry a bufferstatus report (BSR), a power headroom report (PHR), and/or UCI.

FIG. 3 is a block diagram of a base station 310 in communication with aUE 350 in an access network. In the DL, IP packets from the EPC 160 maybe provided to a controller/processor 375. The controller/processor 375implements layer 3 and layer 2 functionality. Layer 3 includes a RRClayer, and layer 2 includes a service data adaptation protocol (SDAP)layer, a packet data convergence protocol (PDCP) layer, a radio linkcontrol (RLC) layer, and a medium access control (MAC) layer. Thecontroller/processor 375 provides RRC layer functionality associatedwith broadcasting of system information (e.g., MIB, SIBs), RRCconnection control (e.g., RRC connection paging, RRC connectionestablishment, RRC connection modification, and RRC connection release),inter radio access technology (RAT) mobility, and measurementconfiguration for UE measurement reporting; PDCP layer functionalityassociated with header compression/decompression, security (ciphering,deciphering, integrity protection, integrity verification), and handoversupport functions; RLC layer functionality associated with the transferof upper layer packet data units (PDUs), error correction through ARQ,concatenation, segmentation, and reassembly of RLC service data units(SDUs), re-segmentation of RLC data PDUs, and reordering of RLC dataPDUs; and MAC layer functionality associated with mapping betweenlogical channels and transport channels, multiplexing of MAC SDUs ontotransport blocks (TBs), demultiplexing of MAC SDUs from TBs, schedulinginformation reporting, error correction through HARQ, priority handling,and logical channel prioritization.

The transmit (TX) processor 316 and the receive (RX) processor 370implement layer 1 functionality associated with various signalprocessing functions. Layer 1, which includes a physical (PHY) layer,may include error detection on the transport channels, forward errorcorrection (FEC) coding/decoding of the transport channels,interleaving, rate matching, mapping onto physical channels,modulation/demodulation of physical channels, and MIMO antennaprocessing. The TX processor 316 handles mapping to signalconstellations based on various modulation schemes (e.g., binaryphase-shift keying (BPSK), quadrature phase-shift keying (QPSK),M-phase-shift keying (M-PSK), M-quadrature amplitude modulation(M-QAM)). The coded and modulated symbols may then be split intoparallel streams. Each stream may then be mapped to an OFDM subcarrier,multiplexed with a reference signal (e.g., pilot) in the time and/orfrequency domain, and then combined together using an Inverse FastFourier Transform (IFFT) to produce a physical channel carrying a timedomain OFDM symbol stream. The OFDM stream is spatially precoded toproduce multiple spatial streams. Channel estimates from a channelestimator 374 may be used to determine the coding and modulation scheme,as well as for spatial processing. The channel estimate may be derivedfrom a reference signal and/or channel condition feedback transmitted bythe UE 350. Each spatial stream may then be provided to a differentantenna 320 via a separate transmitter 318TX. Each transmitter 318TX maymodulate an RF carrier with a respective spatial stream fortransmission.

At the UE 350, each receiver 354RX receives a signal through itsrespective antenna 352. Each receiver 354RX recovers informationmodulated onto an RF carrier and provides the information to the receive(RX) processor 356. The TX processor 368 and the RX processor 356implement layer 1 functionality associated with various signalprocessing functions. The RX processor 356 may perform spatialprocessing on the information to recover any spatial streams destinedfor the UE 350. If multiple spatial streams are destined for the UE 350,they may be combined by the RX processor 356 into a single OFDM symbolstream. The RX processor 356 then converts the OFDM symbol stream fromthe time-domain to the frequency domain using a Fast Fourier Transform(FFT). The frequency domain signal comprises a separate OFDM symbolstream for each subcarrier of the OFDM signal. The symbols on eachsubcarrier, and the reference signal, are recovered and demodulated bydetermining the most likely signal constellation points transmitted bythe base station 310. These soft decisions may be based on channelestimates computed by the channel estimator 358. The soft decisions arethen decoded and deinterleaved to recover the data and control signalsthat were originally transmitted by the base station 310 on the physicalchannel. The data and control signals are then provided to thecontroller/processor 359, which implements layer 3 and layer 2functionality.

The controller/processor 359 can be associated with a memory 360 thatstores program codes and data. The memory 360 may be referred to as acomputer-readable medium. In the UL, the controller/processor 359provides demultiplexing between transport and logical channels, packetreassembly, deciphering, header decompression, and control signalprocessing to recover IP packets from the EPC 160. Thecontroller/processor 359 is also responsible for error detection usingan ACK and/or NACK protocol to support HARQ operations.

Similar to the functionality described in connection with the DLtransmission by the base station 310, the controller/processor 359provides RRC layer functionality associated with system information(e.g., MIB, SIBs) acquisition, RRC connections, and measurementreporting; PDCP layer functionality associated with headercompression/decompression, and security (ciphering, deciphering,integrity protection, integrity verification); RLC layer functionalityassociated with the transfer of upper layer PDUs, error correctionthrough ARQ, concatenation, segmentation, and reassembly of RLC SDUs,re-segmentation of RLC data PDUs, and reordering of RLC data PDUs; andMAC layer functionality associated with mapping between logical channelsand transport channels, multiplexing of MAC SDUs onto TBs,demultiplexing of MAC SDUs from TBs, scheduling information reporting,error correction through HARQ, priority handling, and logical channelprioritization.

Channel estimates derived by a channel estimator 358 from a referencesignal or feedback transmitted by the base station 310 may be used bythe TX processor 368 to select the appropriate coding and modulationschemes, and to facilitate spatial processing. The spatial streamsgenerated by the TX processor 368 may be provided to different antenna352 via separate transmitters 354TX. Each transmitter 354TX may modulatean RF carrier with a respective spatial stream for transmission.

The UL transmission is processed at the base station 310 in a mannersimilar to that described in connection with the receiver function atthe UE 350. Each receiver 318RX receives a signal through its respectiveantenna 320. Each receiver 318RX recovers information modulated onto anRF carrier and provides the information to a RX processor 370.

The controller/processor 375 can be associated with a memory 376 thatstores program codes and data. The memory 376 may be referred to as acomputer-readable medium. In the UL, the controller/processor 375provides demultiplexing between transport and logical channels, packetreassembly, deciphering, header decompression, control signal processingto recover IP packets from the UE 350. IP packets from thecontroller/processor 375 may be provided to the EPC 160. Thecontroller/processor 375 is also responsible for error detection usingan ACK and/or NACK protocol to support HARQ operations.

In some aspects associated with a UE, at least one of the TX processor368, the RX processor 356, and the controller/processor 359 may beconfigured to perform aspects in connection with (198) of FIG. 1. Insome other aspects associated with a base station, at least one of theTX processor 316, the RX processor 370, and the controller/processor 375may be configured to perform aspects in connection with (198) of FIG. 1.

With reference to FIGS. 4-15, various techniques and approachesassociated with RACH procedures are provided. A RACH procedure mayprovide a UE with information that facilitates communication with basestations during initial access, handover between base stations,connection reestablishment, and so forth. For example, a UE may acquireuplink timing synchronization with a base station and/or an uplink grantfor a transmission to the base station based on information obtained viathe RACH procedure.

For some existing RATs, RACH procedures are either contention-free orcontention-based. A contention-free RACH procedure typically involvesthe exchange of three messages between a UE and a base station, e.g.,when the UE is operating in an RRC Connected state, such as when the UEis handed over to the base station. An example message flow of thecontention-free RACH procedure may include assignment of a preamble bythe base station to the UE, transmission of the assigned preamble by theUE to the base station, and transmission of a random access response bythe base station to the UE. The random access response may include atiming advance and/or an uplink grant, based upon which the UE maytransmit uplink data to the base station.

A contention-based RACH procedure typically involves the exchange offour messages between a UE and a base station, e.g., when the UE isinitialing accessing a RAN or reestablishing a connection with the RAN.An example message flow of the contention-based RACH procedure mayinclude transmission of a preamble by the UE to the base station,transmission of a random access response by the base station to the UE,transmission of a connection request message by the UE to the basestation, and transmission of a contention resolution message by the basestation to the UE. While the random access response may include a timingadvance and/or an uplink grant for the UE, the latter two messages maystill be needed for contention resolution between conflicting UEs.

Such contention-free and contention-based RACH procedures may incuroverhead with respectto over-the-air signaling, timing, processing andpower consumption, and so forth. For example, a UE may be unable toinclude data in messages transmitted to the base station for theaforementioned contention-free and contention-based RACH procedures,e.g., because the UE has acquired neither a timing advance nor an uplinkgrant and, if applicable, contention at a base station associated withconflicting UEs is unresolved until completion of the RACH procedure.

FIGS. 4-15 describe a two-step RACH procedure, as well as additionalaspects related to the two-step RACH procedure. In relation to afour-step RACH procedure, for example, both the first and third messages(that is, the preamble and connection request messages, respectively)transmitted by the UE may be combined into a single message, and boththe second and fourth messages (that is, the random access response andcontention resolution messages, respectively) transmitted by the basestation may be combined into a single message. The two-step RACHprocedure may be applicable in 5G NR RANs and/or other mmW and/ornear-mmW RANs.

The two-step RACH procedure may address some overhead issues associatedwith four-step contention-based and/or three-step contention-free RACHprocedures. For example, a UE without valid timing advance may initiatethe two-step RACH procedure with a message that includes an uplink datachannel. Furthermore, the two-step RACH procedure described in thepresent disclosure may be applicable to most or all cell types and sizesoperated by base stations, as well as applicable to most or all RRCstates in which UEs may operate.

As the message flow and structure of the two-step RACH procedure isdifferent from that of three- and four-step RACH procedures, the presentdisclosure may provide for techniques and solutions to configuring theUE for the two-step RACH procedure. Furthermore, the present disclosuremay provide for some approaches to the two-step RACH procedure that maymitigate the overhead commensurate with three- and/or four-step RACHprocedures, such as through reduced latency, reduced over-the-airsignaling, power and/or processing consumption, and so forth.

With reference to FIG. 4, a call flow diagram illustrates a RACHprocedure 410 in a wireless communications system 400. The wirelesscommunications system 400 may include a base station 402 and a UE 404.The base station 402 may provide a cell, on which the UE 404 mayoperate. Some example implementations of the base station 402 may bedescribed with respect to the base station 102/180 of FIG. 1 and/or thebase station 310 of FIG. 3. Some example implementations of the UE 404may be described with respect to the UE 104 of FIG. 1 and/or the UE 350of FIG. 3.

In order to communicate in the wireless communications system 400, theUE 404 may initially access the base station 402 and acquire a timingadvance for transmission of uplink signals to the base station 402. Ifunconnected with the RAN of the base station 402, the UE 404 may performa two-step RACH procedure 410, and furthermore, the base station 402 andthe UE 404 may establish timing synchronization (e.g., uplink timingsynchronization) through the RACH procedure 410. For example, the UE 404may initiate the two-step RACH procedure 410 for initial access in thecell provided by the base station 402, RRC connection reestablishment,handover from another base station to the base station 402,reacquisition of timing synchronization, transition from an RRC Inactivestate, SCell timing alignment, request for Other System Information(OSI), and/or beam failure recovery.

In the wireless communications system 400, the two-step RACH procedure410 may include the exchange of two messages. Specifically, the UE 404may initiate the message exchange of the two-step RACH procedure 410 bysending a first RACH message 414 to the base station 402 and, responsiveto the first RACH message 414, the base station may complete the messageexchange of the RACH procedure 410 by sending a second RACH message 516(also known as a RACH response message) to the UE 404. The first RACHmessage 414 may be referred to as “msgA” and the second RACH message 416may be referred to as “msgB.”

The two-step RACH procedure 410 may be applicable to any size of thecell provided by the base station 402, all RRC states in which the UE404 may operate, and/or whether or not the UE 404 has a valid timingadvance (TA) (e.g., a TA to provide for adjustment of the timing ofuplink transmissions by the UE 404). The two-step RACH procedure 410 maydiffer in some aspects from other RACH procedures, such as RACHprocedures in which four messages are exchanged (e.g., thecontention-based RACH procedure, described supra). However, some aspectsmay be common across the two-step RACH procedure 410 and another RACHprocedure (e.g., the four-step RACH procedure). For example, sequencesassociated with physical RACH (PRACH) and sequences associated with DMRSused for a four-step RACH procedure may also be used for the two-stepRACH procedure 410. Further, a TX chain used for an uplink data channel(e.g., PUSCH) in a four-step RACH procedure may also be used for thetwo-step RACH procedure 410.

According to some aspects, the base station 402 may transmit each of aset of SS/PBCH blocks 418 a-c via a respective one of a set of beams.Thus, each of the SS/PBCH blocks 418 a-c may correspond to one of thebeams of the base station 402. The UE 404 may receive one of more of theset of SS/PBCH blocks 418 a-c, and may acquire downlink timingsynchronization based on the received SS/PBCH blocks 418 a-c (e.g., asdescribed with respect to FIG. 2B, supra).

Further, the base station 402 may transmit configuration information 420associated with operating on the cell provided by the base station 402.The configuration information 420 may be included in one message or maybe separated across two or more messages. In one aspect, the basestation 402 may periodically transmit (e.g., broadcast) theconfiguration information 420, such as in a MIB and/or one or more SIBs(e.g., as described with respect to FIG. 2B, supra). In another aspect,the base station 402 may transmit the configuration information 420 tothe UE via RRC signaling.

The configuration information 420 may include information associatedwith the two-step RACH procedure 410. The configuration information 420may include at least two different RACH request configuration parametersthat each is associated with a respective RRC state in which the UE 404may operate. The UE 404 may receive and decode one or more messages(e.g., a SIB, an RRC message, etc.) carrying the configurationinformation 420 and may perform the RACH procedure 410 based on theconfiguration information 420. For example, the UE 404 may determine atleast one of the at least two different RACH request configurationparameters the corresponds to the RRC state of the UE 404, and the UE404 may perform the RACH procedure 410 using the determined at least oneof the at least two different RACH request configuration parameters.

In some aspects, the configuration information 420 may indicate at leastone configuration associated with the two-step RACH procedure 410 in thetime domain, the frequency domain, or the spatial domain. For example,the configuration information 420 may indicate at least one of a PRACHconfiguration index associated with the two-step RACH procedure 410 inthe time domain, a number of RACH occasions available for the two-stepRACH procedure 410 in the frequency domain, a starting frequencyresource associated with the RACH occasions available for the two-stepRACH procedure 410, a number of preamble sequences per SS/PBCH block,and/or a number of SS/PBCH blocks associated with each of the RACHoccasions available for the two-step RACH procedure 410.

In some further aspects, the configuration information 420 may indicateinformation associated with resource allocation(s) for the msgA 414,sequence configurations associated with a preamble 422 of the msgA 414,modulation and coding schemes (MCSs) associated with the msgA 414, powercontrol schemes associated with the msgA 414 (e.g., at least two powercontrol schemes associated with the msgA 414), a time period associatedwith a gap included in the msgA 414 (e.g., the gap 424, describedinfra), and/or other configuration information.

To initiate the RACH procedure 410, the UE 404 may generate the msgA414. For the RACH procedure 410, the UE 404 may generate the msgA 414 toinclude at least a PRACH preamble 422 and a payload 426. The payload 426may include at least one reference signal 428 and data on an uplink datachannel 430. For example, the at least one reference signal 428 mayinclude a DMRS, and the uplink data channel 430 may be a PUSCH.

According to some configurations, the msgA 414 may include a gap 424 intime between the preamble 422 and the payload 426. For example, the gap424 may be defined as a number of symbols and/or slots inserted betweenthe preamble 422 and the payload 426. The time period of the gap 424 maybe configured at the UE 404 by the base station 402. For example, theconfiguration information 420 may indicate the time period of the gap424, such as by indicating a number of symbols and/or slots that occurbetween the preamble 422 and the payload 426.

With reference to the PRACH preamble 422, the UE 404 may determine aconfiguration for the preamble 422 (e.g., at least one preamblesequence, the preamble SCS, etc.) at least in part based on theconfiguration information 420 and/or at least in part based on one ormore of a size of the payload 426, an MCS configured for the payload426, a type of the cell operated by the base station 402, and/or an RRCstate of the UE 404. In some aspects, the UE 404 may generate thepreamble 422 based on at least one sequence. The at least one sequenceupon which the preamble 422 is based may be described with respect tothe length as either a long sequence or a short sequence.

The payload size of the msgA 414 may be indicated by the preamble 422 ofthe msgA 414. For example, for a specific RRC state, the preamblesequences configured on a RACH occasion may be divided into two groups:group A and group B. Preamble sequences belonging to group A and B maydenote different payload sizes. In some aspects, the minimum payloadsize for RRC IDLE state may be 7 bytes, and the minimum payload size forRRC INACTIVE state may be 9 bytes. Larger payload size may be configuredby the network, and an upper bound for the payload size may beunspecified.

The UE 404 may determine to use at least one of a long sequence or ashort sequence for the preamble 422 based on one or more characteristicsof the UE 404 and/or of the base station 402, such as a bandwidthconfigured for transmission of the preamble 422, the numerology of thepreamble 422, the size of the cell provided by the base station 402(e.g., small cell or macro cell), the RRC state of the UE 404, and/orother characteristic(s). Additionally or alternatively, the UE 404 maydetermine the SCS associated with the preamble 422 based on at least oneof the type of cell operated by the base station 402 and/or the RRCstate of the UE 404.

Illustratively, Table 1 shows PRACH preamble characteristics for a longsequence, which may have a length that is a multiple of 800 microseconds(p), excluding the CP. A long sequence may have a numerology that isdifferent from that of the uplink data channel 430 in the payload 426,and may occupy a bandwidth of 1.08/4.32 MHz. Table 2 shows PRACHpreamble characteristics for a short sequence having a numerology thatis the same as that of the uplink data channel 430 in the payload 426,and occupying a bandwidth of twelve PRBs, e.g., for a frequency range(FR) 1 with 15 kHz/30 kHz SCS and occupying a bandwidth of 2.16/4.32MHz.

TABLE 1 Preamble length Numerology Number of CP length (not includingCP) Format (kHz) Repetitions (μs) (μs) 0 1.25 1 ≈100 800 1 1.25 2 ≈6801600 2 1.25 4 ≈15 3200 3 5 1 ≈100 800

TABLE 2 Preamble length Number of CP length (not including CP) FormatRepetitions (μs) (μs) A1 2 9.4 133 A2 4 18.7 267 A3 6 28.1 400 B1 2 7.0133 B2 4 11.7 267 B3 6 126.4 400 B4 12 30.5 800 C0 1 40.4 66.7 C2 4 66.7267

Referring to the payload 426, the UE 404 may generate the payload 426 toinclude at least one reference signal 428 (e.g., a DMRS) and data on anuplink data channel 430 (e.g., a PUSCH). The at least one referencesignal 428 may be associated with the uplink data channel 430—e.g., theat least one reference signal 428 may be used by a receiver (e.g., thebase station 402) for channel estimation when receiving the uplink datachannel 430. In some aspects, the size of the payload 426 may beassociated with the RRC state of the UE 404.

For the payload 426, the UE 404 may determine at least one of a TB size(e.g., TB size may be 7 bytes, 9 bytes, 40 bytes, or 125 bytes) and/oran MCS (e.g., the MCS may correspond to an index between 0 to 15, with 0to 9 having a modulation order of 2 and 10 to 15 having a modulationorder of 4). Illustratively, the UE 404 may determine the TB size to beone of 7 bytes, 9 bytes, 40 bytes, or 125 bytes. Further, the UE 404 maydetermine the MCS according to an MCS index, modulation order, targetcode rate, and/or spectral efficiency. For example, the UE 404 maydetermine the MCS according to one of Table 3 or Table 4, infra.

TABLE 3 MCS Index Modulation Order Target Code Rate Spectral I_(MCS)Q_(m) R × [1024] Efficiency 0 2 120 0.2344 1 2 157 0.3066 2 2 193 0.37703 2 251 0.4902 4 2 308 0.6016 5 2 379 0.7402 6 2 449 0.8770 7 2 5261.0273 8 2 602 1.1758 9 2 679 1.3262 10 4 340 1.3281 11 4 378 1.4766 124 434 1.6953 13 4 490 1.9141 14 4 553 2.1602 15 4 616 2.4063

TABLE 4 MCS Index Modulation Order Target Code Rate Spectral I_(MCS)Q_(m) R × [1024] Efficiency 0 2 30 0.0586 1 2 40 0.0781 2 2 50 0.0977 32 64 0.1250 4 2 78 0.1523 5 2 99 0.1934 6 2 120 0.2344 7 2 157 0.3066 82 193 0.3770 9 2 251 0.4902 10 2 308 0.6016 11 2 379 0.7402 12 2 4490.8770 13 2 526 1.0273 14 2 602 1.1758 15 4 340 1.3281

In one aspect, the UE 404 may perform one or more downlink measurements(e.g., to measure channel quality, such as reference signal receivedpower (RSRP)) and may determine a state of a buffer of the UE 404 (e.g.,buffer occupancy status) and the QoS of buffered data. Based on the oneor more downlink measurements and/or based on the buffer state, the UE404 may determine the TB size and/or the MCS to be applied to thepayload 426. For example, the UE 404 may adjust the TB size and/or theMCS according to the current channel conditions (indicated by thedownlink measurement(s)) and/or according to the amount of uplink datathe UE 404 is to send to the base station 402 in the uplink data channel430.

In another aspect, the UE 404 may determine the TB size and/or the MCSto be applied to the payload 426 based on the RRC state of the UE 404and/or the size of the cell provided by the base station 402 on whichthe UE 404 operates. For example, the UE 404 may access a table (e.g., alookup table) that indicates correspondence between each of a set of RRCstates and/or cell sizes and a respective MCS and/or TB size to beapplied for transmission of the payload 426. In various aspects, thetable may be predefined in the UE 404 (e.g., stored according to a 3GPPstandard) or may be signaled to the UE 404 from the base station 402(e.g., in at least one SIB). Accordingly, the UE 404 may determine thecurrent RRC state of the UE 404 and/or cell size provided by the basestation 402, and then the UE 404 may refer to the table to determine theMCS and/or TB size that corresponds to the current RRC state and/or cellsize. The UE 404 may then apply the determined MCS and/or TB size to thepayload 426. With this variability, the UE 404 and base station 402 maybenefit from a mechanism for indicating MCS, TB size, and/or payloadsize to the base station 402 by the UE 404.

With the preamble 422 sent separately from the payload 426, the preamble422 may be used to indicate information about the payload 426 (e.g., theat least one reference signal 428 may provide channel estimation for theuplink data channel 430, thus the preamble 422 may be used to conveyinformation other than channel estimation). For example, the UE 404 maygenerate the preamble 422 and/or assign the preamble 422 to a first setof resources in order to indicate the size of the payload 426, the MCSapplied to the payload 426, and/or the TB size used for the payload 426.

In one aspect, the UE 404 may generate the preamble 422 according to asequence configuration that indicates the size of the payload 426, theTB size in the payload 426, and/or the MCS applied to the payload 426.The UE 404 may determine the size of the payload 426, TB size in thepayload 426, and/or MCS, and the UE 404 may determine a sequenceconfiguration that corresponds to the size of the payload 426, TB size,and/or the MCS. For example, the UE 404 may access a table (e.g., alookup table) that indicates correspondence between a respectivesequence configuration and a respective size of the payload 426, TBsize, and/or MCS. The UE 404 may receive information (e.g., table)indicating a respective size of the payload 426, TB size, and/or MCS anda corresponding sequence configuration from the base station 402, suchas in a SIB or RRC message (e.g., in the configuration information 420).

In one aspect, the UE 404 may generate the preamble 422 to indicate thesize of the payload 426, the TB size in the payload 426, and/or the MCSapplied to the payload 426 based on one or more parameters used togenerate the preamble 422. The one or more parameters may include acyclic shift applied to a sequence, a root sequence index used forgeneration of a sequence, another parameter, and/or a combination ofparameters (e.g., a combination of a cyclic shift and a root index).Thus, at least a portion of each possible sequence that the UE 404 maygenerate for the preamble 422 may correspond to at least one of the sizeof the payload 426, the TB size in the payload 426, and/or the MCSapplied to the payload 426. Accordingly, the UE 404 may generate asequence that corresponds to the at least one of the size of the payload426, the TB size in the payload 426, and/or the MCS applied to thepayload 426. By using a corresponding sequence in the preamble 422, theUE 404 may indicate at least one of the size of the payload 426, the TBsize, and/or the MCS to the base station 402.

In another aspect, the UE 404 may determine a sequence configurationassociated with the preamble 422 based on an RRC state of the UE 404and/or a size of the cell on which the UE 404 is operating. For example,the UE 404 may use a short sequence (e.g., length 139) and/or arelatively larger SCS (e.g., 15/30 kHz) when the UE 404 is operating ona small cell and/or when the UE 404 is operating in an RRC Connectedstate. In another example, the UE 404 may use a long sequence (e.g.,length 839) and/or a relatively smaller SCS (e.g., 1.25/5/7.5 kHz) whenthe UE 404 is operating on a larger cell (e.g., macro cell) and/or whenthe UE 404 is operating in an RRC Inactive or RRC Idle state.

With multiple UEs using sequences in preambles to indicate sizes ofpayloads, TB sizes configured in payloads, and/or MCSs configured forpayloads, the probability of collisions may increase—that is, the basestation 402 may be more likely to receive two identical preambles fromtwo different UEs. In order to reduce the probability of preamblecollision, “composite” preambles may be used to increase the pool ofavailable preambles for msgA from different UEs. A composite preamblemay include at least two sequences, and the at least two sequences maybe concatenated in time/frequency, such as by orthogonal cover code(OCC).

For example, the UE 404 may generate the preamble 422 by generating afirst sequence and generating at least one second sequence. The UE 404may concatenate the first sequence and the at least one second sequenceto form the preamble 422. The UE 404 may then send the preamble 422(including the first sequence concatenated with the at least one secondsequence) to the base station 402 by multiplexing the first sequence andthe at least one second sequence. The UE 404 may time-divisionmultiplex, frequency-division multiplex, and/or space-division multiplexthe first sequence and the at least one second sequence to differentiatethe sequences when received by the base station 402.

In some aspects, the UE 404 may indicate at least one of the size of thepayload 426, the TB size in the payload 426, and/or the MCS applied tothe payload 426 using a composite sequence. For example, the combinationof the first sequence and the at least one second sequence may indicateat least one of the size of the payload 426, TB size, and/or MCS. Inanother example, each of the individual first sequence and at least onesecond sequence may indicate one or more of the size of the payload 426,TB size, and/or MCS.

Having generated the preamble 422, the UE 404 may assign the preamble422 to a first set of resources for transmission to the base station 402to initiate the two-step RACH procedure 410. The base station 402 mayallocate specific sets of resources for preamble transmissionsinitiating two-step RACH procedures, and each of the specific sets ofresources may be a RACH occasion. As the base station 402 may beconfigured to receive preamble transmissions on RACH occasions, thefirst set of resources on which to assign the preamble 422 may beassociated with a RACH occasion 412.

According to some aspects, the base station 402 may indicate a set ofRACH occasions, as well as information based upon which the UE 404 canselect the one RACH occasion 412, in the configuration information 420.For example, the UE 404 may determine the first set of resourcesassociated with the RACH occasion 412 based on at least oneconfiguration in the time domain, frequency domain, and/or spatialdomain, as indicated by the configuration information 420.

With respect to time domain configurations, the UE 404 may determine thefirst set of resources associated with the RACH occasion 412 based on aPRACH configuration index indicated in the configuration information420, e.g., for the time-division multiplexing pattern of transmission ofthe preamble 422. The PRACH configuration index may indicate theavailable set of RACH occasions for transmission of the preamble 422,such as a set of subframes available for transmission of the preamble422.

With respect to frequency domain configurations, the UE 404 maydetermine the first set of resources associated with the RACH occasion412 based on a number of RACH occasions indicated in the configurationinformation 420 as available in the frequency domain at the samelocation in the time domain, e.g., for the frequency-divisionmultiplexing pattern of transmission of the preamble 422. Further, theUE 404 may determine a starting frequency resource of the first set ofresources associated with the RACH occasion 412 based on theconfiguration information 420.

With respect to spatial domain configurations, the UE 404 may determinethe RACH occasion 412 associated with the first set of resources inorder to indicate a beam for communication with the base station 402based on the configuration information 420. In some aspects, each RACHoccasion allocated by the base station 402 may be mapped to at least oneof the SS/PBCH blocks 418 a-c, and each of the SS/PBCH blocks 418 a-cmay correspond with a respective beam at the base station 402. The UE404 may determine (e.g., measure) at least one value indicative of thequality of a respective beam based on the corresponding one of theSS/PBCH blocks 418 a-c received via the respective beam. For example,the UE 404 may determine, for each beam via which one of the SS/PBCHblocks 418 a-c is received, one or more of an RSRP, a reference signalreceived quality (RSRQ), a reference signal strength indicator (RSSI), asignal-to-noise ratio (SNR), and/or another similar value.

The UE 404 may determine the beam to be indicated by transmission of thepreamble 422 in the RACH occasion 412 based on the values determinedfrom the SS/PBCH blocks 418 a-c. For example, the UE 404 may select thebeam that corresponds with one of the SS/PBCH blocks 418 a-c having a“best” value (e.g., highest RSRP, highest SNR, etc.). The UE 404 maythen determine the RACH occasion 412 based on the one of the SS/PBCHblocks 418 a-c having the best value. For example, each of the SS/PBCHblocks 418 a-c may be mapped to a respective RACH occasion, and the UE404 may select one RACH occasion 412 to indicate the selected beam basedon the mapping between RACH occasions and SS/PBCH blocks 418 a-c.

In one configuration, the UE 404 may determine the mapping between theselected one of the SS/PBCH blocks 418 a-c and the RACH occasion 412associated with the first set of resources further based on theindications in the configuration information 420 of a number of preamblesequences per SS/PBCH block and/or a number of SS/PBCH blocks associatedwith each of the RACH occasions. Rules and/or other information formappings to indicate a beam selected by the UE 404 may be preconfigured(e.g., stored according to a 3GPP standard) or may be signaled to the UE404 from the base station 402.

According to some other aspects, UE 404 may assign the preamble 422 tothe first set of resources based on at least one of the size of thepayload 426, the TB size in the payload 426, and/or the MCS applied tothe payload 426. Accordingly, the first set of resources to which thepreamble 422 is assigned may indicate the at least one of the size ofthe payload 426, the TB size in the payload 426, and/or the MCS appliedto the payload 426 when the base station 402 receives the preamble 422.

In one aspect, the UE 404 may determine the first set of resources basedon information that indicates correspondence between sets of resourcesand the at least one of the size of the payload 426, the TB size in thepayload 426, and/or the MCS applied to the payload 426. For example, theUE 404 may access a table (e.g., a lookup table) that indicates thecorrespondence between sets of resources and the at least one of thesize of the payload 426, TB size, and/or MCS. In various aspects, theinformation (e.g., table) may be predefined in the UE 404 (e.g., storedaccording to a 3GPP standard) or may be signaled to the UE 404 from thebase station 402 (e.g., in at least one SIB).

With the preamble 422 separate from the payload 426, the UE 404 mayassign the payload 426 to a second set of resources. The second set ofresources may be based on a size of the cell on which the UE 404 isoperating and/or the RRC state in which the UE 404 is operating.Accordingly, the UE 404 may determine at least one of the cell size ofthe base station 402 and/or the RRC state of the UE 404, and the UE 404may determine a second set of resources that corresponds to the at leastone of the cell size of the base station 402 and/or the RRC state of theUE 404.

In one aspect, the UE 404 may determine the second set of resourcesbased on information that indicates correspondence between sets ofresources and the at least one of the size of the cell on which the UE404 is operating and/or the RRC state in which the UE 404 is operating.For example, the UE 404 may access a table (e.g., a lookup table) thatindicates the correspondence between sets of resources and the at leastone of the size of the cell on which the UE 404 is operating and/or theRRC state in which the UE 404 is operating. In another example, thesecond set of resources may be a function (e.g., mathematical function)of the at least one of the size of the cell on which the UE 404 isoperating and/or the RRC state in which the UE 404 is operating. The UE404 may evaluate the function with the cell size and RRC state as inputsin order to obtain the second set of resources. In various aspects, theinformation (e.g., table, function, etc.) may be predefined in the UE404 (e.g., stored according to a 3GPP standard) or may be signaled tothe UE 404 from the base station 402 (e.g., in at least one SIB).

The UE 404 may be identified by the base station 402 according to anidentifier (ID) of the UE 404, such as a radio network temporaryidentifier (RNTI) (e.g., a random access (RA) RNTI, a temporary RNTI,etc.). The msgA 414 may be the first transmission by the UE 404 to thebase station 402 and, therefore, the base station 402 may benefit from amechanism for indicating the ID of the UE 404 to the base station 402 inthe msgA 414, particularly because the msgA 414 may include data fromthe UE 404 in the payload 426. Accordingly, the UE 404 may indicate anID of the UE 404 using one or more (or a combination of) approaches forincluding information in the msgA 414.

In one aspect, the UE 404 may indicate an ID of the UE 404 based on thesequence of the preamble 422. For example, a sequence index used by theUE 404 for generating the sequence of the preamble 422 may indicate theID of the UE 404. In one aspect, different root sequence indexes maycorrespond to different IDs or different bits of an ID. The UE 404 maydetermine an ID of the UE 404, and the UE 404 may determine a rootsequence index for generating the preamble 422 based on the ID of the UE404. The UE 404 may access information that indicates correspondencebetween ID information (e.g., sets of bits) and the different rootsequence indexes. For example, the UE 404 may access a table (e.g., alookup table) that indicates the correspondence between ID information(e.g., sets of bits) and the different root sequence indexes. The UE 404may generate a sequence for the preamble 422 from a root sequence indexthat corresponds to the ID information to be conveyed by the UE 404 tothe base station 402.

In another aspect, the UE 404 may indicate an ID of the UE 404 based ona composite sequence of the preamble 422. For example, a combination ofsequences and/or a combination of sequence parameters (e.g., cyclicshifts, root sequence indexes, etc.) used by the UE 404 for thecomposite sequence of the preamble 422 may indicate ID information(e.g., a set of bits) of the UE 404. The UE 404 may access informationthat indicates correspondence between ID information (e.g., sets ofbits) and composite sequences. Accordingly, the UE 404 may generate acomposite sequence for the preamble 422 that corresponds to IDinformation to be conveyed by the UE 404 to the base station 402.

In one aspect, the UE 404 may indicate an ID of the UE 404 based on thesequence of the at least one reference signal 428. For example, a DMRSsequence index used by the UE 404 for generating the at least onereference signal 428 may indicate the ID of the UE 404. In one aspect,different DMRS sequence indexes may correspond to different IDs ordifferent bits of an ID. The UE 404 may determine an ID of the UE 404,and the UE 404 may determine a DMRS sequence index for generating the atleast one reference signal 428 based on the ID of the UE 404. The UE 404may access information that indicates correspondence between IDinformation (e.g., sets of bits) and the different DMRS sequenceindexes. For example, the UE 404 may access a table (e.g., a lookuptable) that indicates the correspondence between ID information (e.g.,sets of bits) and the different DMRS sequence indexes. The UE 404 maygenerate a sequence for the at least one reference signal 428 from aDMRS sequence index that corresponds to the ID information to beconveyed by the UE 404 to the base station 402.

In another aspect, the UE 404 may indicate an ID of the UE 404 using aportion of the bits in the payload 426. For example, a portion of thebits of the payload 426 may be reserved for indicating ID informationassociated with the UE 404. Accordingly, the UE 404 may set the portionof the bits in the payload 426 to values indicating at least a portionof the ID information associated with the UE 404.

In another aspect, the UE 404 may indicate an ID of the UE 404 using ascrambling code that is used to scramble the payload 426. For example, ascrambling code used by the UE 404 for scrambling the payload 426 mayindicate the ID of the UE 404. In one aspect, different scrambling codesmay correspond to different IDs or different bits of an ID. The UE 404may determine an ID of the UE 404, and the UE 404 may determine ascrambling code for scrambling the payload 426 based on the ID of the UE404. The UE 404 may then use the determined scrambling code forscrambling the payload 426 in order to indicate ID information (e.g., aset of bits of the ID of the UE 404) associated with the UE 404 to thebase station 402.

In another aspect, the UE 404 may indicate an ID of the UE 404 using acyclic redundancy check (CRC) mask. For example, a mask used by the UE404 for masking the CRC included in the msgA 414 may indicate the ID ofthe UE 404. In one aspect, different CRC masks may correspond todifferent IDs or different bits of an ID. The UE 404 may determine an IDof the UE 404, and the UE 404 may determine a mask used by the UE 404for masking the CRC included in the msgA 414 based on the ID of the UE404. The UE 404 may then mask the CRC included in the msgA 414 using thedetermined CRC mask in order to indicate ID information (e.g., a set ofbits of the ID of the UE 404) associated with the UE 404 to the basestation 402.

In one aspect, the UE 404 may use a combination of two or more of theaforementioned techniques for conveying ID information in order toindicate an ID of the UE 404 to the base station 402. For example, aroot sequence index used for generation of the sequence for the preamble422 may indicate a first set of bits and a second set of bits may beindicated in the payload 426. The base station 402 may combine the firstset of bits and the second set of bits in order to obtain the full ID ofthe UE 404.

With the generated preamble 422 and the generated payload 426, the UE404 may send the msgA 414 to the base station 402. The UE 404 may sendthe msgA 414 by first sending the preamble 422 and then sending thepayload 426. When the UE 404 sends the payload 426, the reference signal428 and the uplink data channel 430 may be in the same slot and may havethe same bandwidth.

The UE 404 may send the payload 426 of the msgA 414 with or withoutfrequency hopping in the uplink data channel 430. With or withouthopping in the uplink data channel 430, the UE 404 may frontload a firstof the at least one reference signal 428. Specifically, the UE 404 mayassign the first of the at least one reference signal 428 to one of twopossible locations: the first OFDM symbol or the third/fourth symbol ofthe slot in which the first of the at least one reference signal 428 andthe uplink data channel 430 are sent.

The UE 404 may assign the at least one reference signal 428 to one ormore symbols that are the same for the uplink data channel 430 withCP-OFDM and DFT-s-OFDM without frequency hopping. In one aspect, the UE404 may frontload the at least one reference signal 428 according to aDMRS configuration type 1, which may support up to eight ports. WithDMRS configuration type 1, the at least one reference signal 428 may beassigned to resource(s) with an interleaved frequency divisionmultiplexing (IFDM)-based pattern having a Comb-2 pattern with CSs,assigned to one OFDM symbol having a Comb-2 pattern with two CSs for upto four ports, and/or assigned to two OFDM symbols having a Comb-2pattern with two CSs and time domain (TD) OCC (TD-OCC) ({1 1} and {1−1}) for up to eight ports. If the number of ports for the at least onereference signal 428 is less than or equal to four, the number offrontloaded DMRS symbols may be one or two. For the at least onereference signal 428 for CP-OFDM with extended CP (e.g., at least 60 kHzSCS), the DMRS configuration type 1 as with normal CP may be supported.In some cases, the OCC can be applied in both the time and frequencydomains to increase the pool size available for the at least onereference signal 428 (e.g., DMRS).

In another aspect, the UE 404 may frontload the at least one referencesignal 428 according to DMRS configuration type 2, which may support upto twelve ports. With DMRS configuration type 2, the at least onereference signal 428 may be assigned according to a frequency domain(FD) OCC (FD-OCC) pattern with adjacent REs in the frequency domain.With one OFDM symbol for the at least one reference signal 428, the atleast one reference signal 428 may be assigned according to 2-FD-OCCacross adjacent REs in the frequency domain for up to six ports. Withtwo OFDM symbols for the at least one reference signal 428, the at leastone reference signal 428 may be assigned according to 2-FD-OCC acrossadjacent REs in the frequency domain and TD-OCC (both {1 1} and {1 −1})for up to twelve ports. If the number of ports for the at least onereference signal 428 is less than or equal to six, the number offrontloaded DMRS symbols may be one or two. In some cases, the OCC canbe applied in both the time and frequency domains to increase the poolsize available for the at least one reference signal 428 (e.g., DMRS).

As illustrated, the UE 404 may insert a gap 424 in time when sending themsgA 414. The time duration of the gap 424 may be configurable by thebase station 402 (e.g., in the configuration information 420), and canbe zero, a fraction of an OFDM symbol, one or more OFDM symbols, or oneor more slots. The gap 424 may facilitate transmission of the msgA 414when the preamble 422 and the payload 426 differ in various ways. Forexample, the gap 424 the time gap may be split into a slot-level offsetwith a range of {1, 2, . . . , 32} and a symbol-level offset with arange of {0, 1, 2, . . . , 13}.

In one aspect, the UE 404 may transmit the msgA 414 so that the preamble422 occupies a different bandwidth portion than the payload 426(although the bandwidth portion occupied by the preamble 422 may atleast partially overlap with the bandwidth portion occupied by thepayload 426). For example, the preamble 422 may occupy a relativelysmaller bandwidth than the payload 426. In another aspect, the UE 404may transmit the msgA 414 so that the preamble 422 has a differentnumerology than the payload 426. For example, the UE 404 may transmitthe msgA 414 so that the SCS and/or sampling rate of the preamble 422 isdifferent from that of the payload 426. In still another aspect, the UE404 may transmit the msgA 414 so that the preamble 422 is transmitted ona beam that is different than a beam on which the payload 426 istransmitted.

The UE 404 may transmit the msgA 414 using at least one power controlscheme of the at least two different power control schemes indicated inthe configuration information 420. The UE 404 may determine the at leastone power control scheme to be used for msgA 414 transmission based onthe MCS configured for the payload 426. According to one configuration,the UE 404 may determine to use two different power control schemes formsgA 414 transmission—that is, the UE 404 may implement different powercontrol schemes for the transmission of the preamble 422 and thetransmission of the payload 426. For example, the UE 404 may transmitthe preamble 422 according to a power control scheme that power ramps orincreases transmission power as the preamble 422 is transmitted (andpotentially retransmitted), whereas the UE 404 may transmit the payload426 with a power control scheme that is based on an MCS configured forthe payload 426. The preamble 422 does not include any data to which anMCS can be applied, and therefore, an MCS-dependent power control schememay be inapplicable to the preamble 422.

The base station 402 may receive the msgA 414 from the UE 404 initiatingthe RACH procedure 410. Depending upon the one or two power controlschemes used by the UE 404 for transmission of the msgA 414, the basestation 402 may receive the preamble 422 with a different (e.g.,greater) power than that with which the payload 426 is received. Forexample, the base station 402 may receive the preamble 422 according toone power control scheme that defines the initial transmission power forthe preamble 422, and another power control scheme that indicates thetransmission power for the payload 426 is dependent upon the MCSconfigured for the payload 426.

When the base station 402 receives the preamble 422, the base station402 may determine the configuration of the sequence (or sequences, ifconcatenated). Specifically, the base station 402 may determine thelength of the sequence and/or the SCS configured for the preamble 422.At least one of the sequence length included in the preamble 422 and/orthe SCS configured for the preamble 422 may be based on the type of celloperated by the base station 402 and/or the RRC state of the UE 404. Forexample, the base station 402 may determine that the preamble 422includes a short sequence (e.g., length 139) and/or is configured with arelatively larger SCS (e.g., 15/30 kHz) when the base station 402provides a small cell and/or when the UE 404 is operating in an RRCConnected state. In another example, the base station 402 may determinethat the preamble 422 includes a long sequence (e.g., length 839) and/ora relatively smaller SCS (e.g., 1.25/5/7.5 kHz) when the base station402 provides a larger cell (e.g., macro cell) and/or when the UE 404 isoperating in an RRC Inactive or RRC Idle state.

The base station 402 may receive the preamble 422 on the first set ofresources associated with the RACH occasion 412. In one aspect, the basestation 402 may determine at least one of the size of the payload 426,the TB size configured for the payload 426, and/or the MCS configuredfor the payload 426 based on receiving the preamble 422. For example,the base station 402 may access information indicating a correspondencebetween sequence configurations and/or sets of resources and at leastone of payload sizes, TB sizes, and/or MCSs. As described, supra, thesequence configuration of the preamble 422 and/or the first set ofresources may indicate the at least one of the size of the payload 426,TB size configured for the payload 426, and/or MCS configured for thepayload 426. Based on the information indicating the correspondence, thebase station 402 may determine the at least one of the size of thepayload 426, TB size configured for the payload 426, and/or MCSconfigured for the payload 426.

Based on the preamble 422, the base station 402 may receive and decodethe payload 426. In some aspects, the gap 424 in time may facilitate thedecoding by the base station 402, e.g., by allowing the base station 402a period of time to adjust a processing window to correspond to the TBsize, adjust the data rate to correspond to the MCS, allocate processingtime for a size of the payload 426, etc.

In one aspect, the base station 402 may determine the RRC state of theUE 404 based on at least one of the size of the payload 426 and/or theMCS configured for the payload 426. For example, the base station 402may access information indicating correspondence of one or more payloadsizes and/or MCSs with RRC states. Based on the information indicatingthe correspondence, the base station 402 may determine the RRC state ofthe UE 404 by determining the corresponding one of the size of thepayload 426 and/or MCS configured for the payload 426.

In still another aspect, the base station 402 may determine a beamselected by the UE 404 based on receiving the preamble 422 on the firstset of resources associated with the RACH occasion 412. For example, theRACH occasion 412 in which the preamble 422 is received may be mapped toa beam at the base station 402. Each RACH occasion allocated by the basestation 402 may be mapped to at least one of the SS/PBCH blocks 418 a-c,and each of the SS/PBCH blocks 418 a-c may correspond with a respectivebeam at the base station 402. The base station 402 may determine a beamselected by the UE 404 for communication based on the at least one ofthe SS/PBCH blocks 418 a-c that is mapped to the RACH occasion 412.

The mapping between the RACH occasion 412 and the at least one of theSS/PBCH blocks 418 a-c may be based on the number of RACH occasionsavailable in the frequency for the two-step RACH procedure 410, thenumber of preamble sequences per each of the SS/PBCH blocks 418 a-c, thenumber of SS/PBCH blocks associated with each RACH occasion, and/orother similar information, which may be indicated in the configurationinformation 420. Rules and/or other information for mappings associatedwith the determination by the base station 402 of the beam selected bythe UE 404 may be preconfigured at the base station 402 (e.g., storedaccording to a 3GPP standard).

Further, in order to identify the source of the msgA 414, the basestation 402 may determine the ID of the UE 404. The base station 402 maydetermine the ID of the UE 404 based on one or more of (or a combinationof) a preamble sequence index associated with the preamble 422, a DMRSsequence index associated with the at least one reference signal 428 inthe payload 426, a subset set of a set of bits in the payload 426, ascrambling code applied to the payload, and/or a mask applied to a CRCincluded in the msgA 414.

In response to the msgA 414, the base station 402 may generate a msgB416. The base station 402 may generate the msgB 416 to include controlinformation on a downlink control channel 432 (e.g., a PDCCH) and dataon a downlink data channel (e.g., a PDSCH). The base station 402 maysend the msgB 416 to the UE 404 to complete the RACH procedure 410. TheUE 404 may receive the msgB 416, and the UE 404 may acquire uplinktiming synchronization based on the msgB 416.

Now referring to FIG. 5, illustrates a TX chain 500 associated withtransmission of a msgA 524 from a UE to a base station. For example, themsgA 524 may be the msgA 414 sent by the UE 404 to the base station 402,as illustrated in FIG. 4. A UE may generate a payload 502 of a msgA. Thepayload 502 may include uplink data to be transmitted by the UE to abase station. For example, the payload 502 may include data retrievedfrom a buffer of the UE. In some aspects, the size of the payload 502may be associated with an RRC state of the UE. The payload 502 may beprovided to the TX chain 500 for transmission to the base station.

In the TX chain 500, a low-density parity-check (LDPC) channel encoder504 may generate and apply error correcting code to the payload 502.Further, bit scrambling 506 may be applied to the payload 502 in orderto provide a level of encryption to the payload 502.

The payload 502 may be modulated with linear modulation 508 to generatea waveform for the payload 502. If enable, transform precoding 510 maybe applied, which may generate complex-valued symbols for the payload502. Next, the payload 502 may be mapped to REs on a grid according toRE mapping 512. An IFFT 514 may be applied to produce an uplink datachannel 532 (e.g., a PUSCH) carrying a time domain OFDM symbol streamfor the payload 502.

A multiplexer (MUX) 516 may then multiplex the uplink data channel 532(carrying the payload 502) with at least one reference signal 520 (e.g.,at least one DMRS) in the time and/or frequency domain, e.g., to providefor channel estimation. In some aspects, the multiplexed uplink datachannel/reference signal 530 may be assigned to TBs and an MCS may beapplied thereto. The MCS and/or the size of the TBs may be configuredbased on an RRC state in which the UE is operating and/or based on asize of the cell on which the UE is operating. For example, a table(e.g., a lookup table) may indicate a respective TB size and/or MCSconfiguration for each RRC state and/or cell size and, according to theRRC state of the UE and/or cell size, the TB size and MCS for the uplinkdata channel/reference signal 530 may be configured. The uplink datachannel/reference signal 530 may be provided for radio resource mapping518.

A preamble 522 may be generated in association with the uplink datachannel/reference signal 530. In one aspect, the preamble 522 may begenerated based on the uplink data channel/reference signal 530. Forexample, the preamble 522 may be generated based on a sequenceconfiguration that corresponds to the TB size, MCS, size of the payload502, and/or RRC state of the UE. In some aspects, the sequenceconfiguration may include a cyclic shift, root sequence index, and/orcombination thereof for generation of the preamble 522 that correspondsto at least one of the TB size, MCS, and/or size of the payload 502. Insome other aspects, at least one of the length of the sequence and/orthe SCS configured for the preamble 522 may be based on at least one ofthe type of cell operated by the base station and/or the RRC state ofthe UE. The sequence configuration may be signaled to the UE by the basestation in a SIB or via RRC signaling.

In some aspects, the preamble 522 may be comprised of a plurality ofsequences. For example, multiple sequences may be concatenated in thetime and/or frequency domain (e.g., by OCC) to construct a “composite”preamble. Each of the individual sequences may be generated using a rootsequence index and cyclic shift(s), and then the individual sequencesmay be time-division multiplexed, frequency-division multiplexed, and/orspace-division multiplexed.

At the radio resource mapping 518, the preamble 522 may be assigned to afirst set of resources associated with a RACH occasion. In one aspect,the first set of resources associated with the RACH occasion may bedetermined based on a beam selected by the UE. That is, the UE mayselect a “good” or “best” beam for communication with the base station,such as a beam via which an SS/PBCH block having a highest RSRP isreceived or a beam via which an SS/PBCH block having an RSRP thatsatisfies a threshold is received. The UE may indicate the selected beamto the base station by mapping information indicating the selected beam(e.g., an SS/PBCH block corresponding to the selected beam) to the RACHoccasion associated with the first set of resources.

In some other aspects, the first set of resources associated with theRACH occasion may be allocated based on the uplink datachannel/reference signal 530. For example, the first set of resourcesmay be allocated for the preamble 522 based on at least one of the TBsize, MCS, and/or size of the payload 502. The first set of resources onwhich the preamble 522 is carried may correspond to at least one of theTB size, MCS, and/or size of the payload 502 and, therefore, the firstset of resources may indicate the at least one of the TB size, MCS,and/or size of the payload 502. The corresponding resource allocationfor the first set of resources to indicate the at least one of the TBsize, MCS, and/or size of the payload 502 may be signaled to the UE in aSIB or via RRC signaling.

Further at the radio resource mapping 518, the uplink datachannel/reference signal 530 may be mapped to a second set of resources,which may be allocated based on a size of a cell on which the UE isoperating and/or based on an RRC state in which the UE is operating. Insome aspects, the resource allocation for the second set of resourcesmay be signaled by a SIB or via RRC signaling from a base station to theUE, may be predefined by a math function, or may be predefined by atable (e.g., lookup table) with respect to the preamble 522.

The preamble 522 and the uplink data channel/reference signal 530(carrying the payload 502) may be time-division multiplexed so that thepreamble 522 is transmitted on the first set of resources associatedwith the RACH occasion before the uplink data channel/reference signal530 is transmitted on the second set of resources.

In some aspects, a gap in time may be inserted between the preamble 522and the uplink data channel/reference signal 530 at the radio resourcemapping 518. The gap may be configurable at the UE by the base station,such as via a SIB or RRC signaling. The gap may be a number of slots(including fractions), a number of symbols (including fractions), orzero.

In the aggregate, the preamble 522 and uplink data channel/referencesignal 530 (and optional gap) may comprise the msgA 524 of a RACHprocedure (e.g., two-step RACH procedure). Subsequently, the TX chain500 may apply the signal representing the preamble 522 to an antenna fortransmission on the first set of resources associated with the RACHoccasion and may apply the signal representing the uplink datachannel/reference signal 530 to the antenna for transmission on thesecond set of resources.

The msgA 524 may be transmitted using at least one of at least twodifferent power control schemes configured at the UE by the basestation. For example, a first power control scheme may define an initialtransmission power and a power ramping step for retransmissions, whereasa second power control scheme may be dependent upon an MCS configuredfor the uplink data channel/reference signal 530 (in which the payload502 is carried). The first power control scheme may be used fortransmission of the preamble 522, while the second (MCS-dependent) powercontrol scheme may be used for transmission of the uplink datachannel/reference signal 530.

In some aspects, the preamble 522 may occupy a different bandwidthportion than the uplink data channel/reference signal. In addition, thepreamble 522 may be transmitted on a different beam than the uplink datachannel/reference signal 530. Further, the numerology (e.g., SCS) withwhich the preamble 522 is transmitted may be different than that withwhich the uplink data channel/reference signal 530 is transmitted.

Turning to FIG. 6, a block diagram illustrates resource allocations andsequence configurations for preambles transmitted by UEs in RACHprocedures (e.g., two-step RACH procedures). In various aspects, twopreamble sets 602, 604 may be transmitted (e.g., by different UEs)—e.g.,a preamble set may include a set of sequences, such as a set ofsequences generated according to a root sequence index within a firstrange and/or a number of cyclic shifts within a second range. The firstpreamble set 602 may be associated with a first TB size and/or MCSconfiguration, whereas the second preamble set 604 may be associatedwith a second TB size and/or MCS configuration. For example, a preamblecorresponding to the first preamble set 602 may be used by UEs toindicate a msgA includes a payload having a first TB size and first MCS,whereas a preamble corresponding to the second preamble set 604 may beused by other UEs to indicate a msgA includes a payload having a secondTB size and a second MCS.

A UE (e.g., the UE 404) may transmit a preamble (e.g., the preamble 422)corresponding to the first preamble set 602 or the second preamble set604 during a preamble transmission occasion (e.g., a RACH occasion),which may be followed in time (e.g., after an optional gap) by a payloadtransmission occasion during which the UE may transmit a payload (e.g.,the payload 426). The UE may transmit a msgA (e.g., the msgA 414) for aRACH procedure (e.g., the two-step RACH procedure 410) by transmittingthe preamble in the preamble transmission occasion (e.g., the RACHoccasion 412) and transmitting the payload in the payload transmissionoccasion.

According to a first configuration 600, the first preamble set 602 maybe separated from the second preamble set 604 by frequency and/orspace/beam but may at least partially overlap in time. For example, apreamble of the first preamble set 602 may be time-division multiplexedon a wireless channel with a preamble of the second preamble set 604.

In some aspects, a preamble of the first preamble set 602 may be carriedin a first set of subcarriers, whereas a preamble of the second preambleset 604 may be carried in a second set of subcarriers that does notoverlap with the first set of subcarriers. However, a preamble of thefirst preamble set 602 may be carried in a first set of set of symbolsoccurring during a first portion of the preamble transmission occasion,and a preamble of the second preamble set 604 may be carried in a secondset of symbols occurring at least partially in the first portion of thepreamble transmission occasion.

In some aspects, in order to indicate the first TB size and/or firstMCS, a UE would assign a preamble to a first set of REs comprised of thefirst set of subcarriers and the first set of symbols. Similarly, inorder to indicate the second TB size and/or second MCS, a UE wouldassign a preamble to a second set of REs comprised of the second set ofsubcarriers and the second set of symbols. Because preambles of thefirst preamble set 602 may be distinguishable from those of the secondpreamble set 604 based on subcarrier allocation, the sequenceconfigurations for the first preamble set 602 may at least partiallyoverlap with that of the second preamble set 604 (e.g., a preamblegenerated for the first preamble set 602 may be the same as a preamblegenerated for the second preamble set 604).

According to a second configuration 620, the first preamble set 602 maybe separated from the second preamble set 604 in time but may at leastpartially overlap in frequency and/or space/beam. For example, apreamble of the first preamble set 602 may be frequency-divisionmultiplexed on a wireless channel with a preamble of the second preambleset 604.

In some aspects, a preamble of the first preamble set 602 may be carriedin a first set of subcarriers, and a preamble of the second preamble set604 may be at least partially carried in the first set of subcarriers.However, a preamble of the first preamble set 602 may be carried in afirst set of set of symbols during a first portion of the preambletransmission occasion, whereas a preamble of the second preamble set 604may be carried in a second set of symbols during a second portion of thepreamble transmission occasion that does not overlap with the firstportion.

Thus, in order to indicate the first TB size and/or first MCS, a UEwould generate a preamble of the first preamble set 602 and/or assign apreamble to a first set of REs comprised of the first set of subcarriersand the first set of symbols. Similarly, in order to indicate the secondTB size and second MCS, a UE would generate a preamble of the secondpreamble set 604 and/or assign a preamble to a second set of REscomprised of the second set of subcarriers and the second set ofsymbols. Because preambles of the first preamble set 602 may bedistinguishable from those of the second preamble set 604 based onsymbol allocation, the sequence configurations for the first preambleset 602 may at least partially overlap with that of the second preambleset 604 (e.g., a preamble generated for the first preamble set 602 maybe the same as a preamble generated for the second preamble set 604).

According to a third configuration 640, the first preamble set 602 maybe separated from the second preamble set 604 by sequence configuration,but may at least partially overlap in time and in frequency and/orspace/beam. For example, a preamble of the first preamble set 602 may becode-division multiplexed on a wireless channel with a preamble of thesecond preamble set 604.

In some aspects, a preamble of the first preamble set 602 may begenerated according to a first set of RACH parameters, such as a firstroot sequence index and/or a first number of cyclic shifts. However,preambles of the second preamble set 604 may be generated according to asecond set of RACH parameters that includes a different root sequenceindex and/or a different number of cyclic shifts. Because preambles aredistinguishable based on whether the preamble was generated according tothe sequence configuration for the first preamble set 602 or the secondpreamble set 604, preambles of the first preamble set 602 and the secondpreamble set 604 may overlap in time and/or frequency or space/beam.Thus, a preamble of the first preamble set 602 may occur on a first setof time/frequency resources, and a preamble of the second preamble set604 may also occur at least partially on the first set of time/frequencyresources.

In order to indicate the first TB size and/or first MCS, a UE wouldgenerate a preamble according to the sequence configuration of the firstpreamble set 602. Similarly, in order to indicate the second TB size andsecond MCS, a UE would generate a preamble according to the sequenceconfiguration of the second preamble set 604. Because preambles of thefirst preamble set 602 may be distinguishable from those of the secondpreamble set 604 based on their respective sequence configurations, thetime/frequency resources allocated for the first preamble set 602 may atleast partially overlap with those allocation for the second preambleset 604 (e.g., a preamble generated for the first preamble set 602 maybe allocated resources that at least partially overlap with resourcesallocated for a preamble generated for the second preamble set 604).

FIG. 7 illustrates a block diagram of configurations 700, 720 ofcomposite sequences. In the context of FIG. 4, the UE 404 may generatethe preamble 422 to include a plurality of sequences 702 a, 702 b, 702m. The UE 404 may then transmit the msgA 414 including the plurality ofsequences 702 a, 702 b, 702 m as the preamble 422 during the RACHoccasion 412 (e.g., a preamble transmission occasion). Followingtransmission of the preamble 422, the UE 404 may transmit the payload426 during the payload transmission occasion.

According to the first configuration 700, a UE may generate threesequences 702 a, 702 b, 702 m. The sequences 702 a, 702 b, 702 m may berespectively generated according to three different sequenceconfigurations—e.g., three different sequence configurations that differwith respect to at least one of a root sequence index and/or a number ofcyclic shifts. The UE may concatenate the sequences 702 a, 702 b, 702 m,e.g., using OCC. To distinguish the sequences 702 a, 702 b, 702 m fromone another, the UE may time-division multiplex the sequences 702 a, 702b, 702 m. Accordingly, the UE may transmit a first sequence 702 a duringa first portion of the preamble transmission occasion, a second sequence702 b during a second portion of the preamble transmission occasion, andan m^(th) sequence 702 m during an m^(th) portion of the preambletransmission occasion. In some aspects, the sequences 702 a, 702 b, 702m may occupy the same set of subcarriers and/or may be transmitted onthe same beam(s).

A UE may generate three sequences 702 a, 702 b, 702 m. The sequences 702a, 702 b, 702 m may be respectively generated according to the samesequence configuration or different sequence configurations—e.g.,sequence configurations that differ with respect to at least one of aroot sequence index and/or a number of cyclic shifts. The UE mayconcatenate the sequences 702 a, 702 b, 702 m, e.g., using OCC.

According to the first configuration 700, to distinguish the sequences702 a, 702 b, 702 m from one another, the UE may time-division multiplexthe sequences 702 a, 702 b, 702 m. Accordingly, the UE may transmit afirst sequence 702 a during a first portion of the preamble transmissionoccasion, a second sequence 702 b during a second portion of thepreamble transmission occasion, and an m^(th) sequence 702 m during anm^(th) portion of the preamble transmission occasion. In some aspects,the sequences 702 a, 702 b, 702 m may occupy the same set of subcarriersand/or may be transmitted on the same beam(s).

According to the second configuration 720, to distinguish the sequences702 a, 702 b, 702 m from one another, the UE may frequency-divisionmultiplex and/or space-division multiplex the sequences 702 a, 702 b,702 m. Accordingly, the UE may transmit a first sequence 702 a in afirst set of subcarriers and/or on a first beam, a second sequence 702 bin a second set of subcarriers and/or on a second beam, and an m^(th)sequence 702 m in an m^(th) set of subcarriers and/or on an m^(th) beam.In some aspects, sequences 702 a, 702 b, 702 m may at least partiallyoccur during the same time during the preamble transmission occasion.

FIG. 8 is a flowchart of a method 800 of wireless communication. Themethod 800 may be performed by a UE (e.g., the UE 104, 350, 404; theapparatus 1202/1202′; the processing system 1314, which may include thememory 360 and which may be the entire UE 104, 350, 404 or a componentof the UE 104, 350, 404, such as the TX processor 368, the RX processor356, and/or the controller/processor 359). One or more of theillustrated operations may be omitted, transposed, or contemporaneous.Various optional operations may be illustrated with dashed lines.

At operation 802, the UE may receive configuration information from abase station. The UE may receive the configuration information in atleast one of a SIB or an RRC message from the base station. In someaspects, the configuration information may be received in two or moremessages. For example, referring to FIG. 4, the UE 404 may receive theconfiguration information 420 from the base station 402.

The configuration information may at least two different RACH requestconfiguration parameters associated with transmission of a first messagefor a two-step RACH procedure. Each of the at least two different RACHrequest configuration parameters may be associated with a respective RRCstate, such as RRC Idle, RRC Inactive, or RRC Connected. For example,the configuration information may indicate at least two differentpreamble groups, at least two different payload sizes, at least twodifferent MCSs, at least two different time and frequency resourceallocations, and/or or at least two different power control schemes.According to various aspects, the configuration information may furtherindicate a number of RACH occasions available for the RACH procedure, astarting frequency resource associated with the RACH occasions, a numberof preamble sequences per SS/PBCH block, and/or a number of SS/PBCHblocks associated with each of the RACH occasions.

At operation 804, the UE may generate a first message associated withRACH procedure including a preamble and a payload. For example, thefirst message may be a msgA of a two-step RACH procedure. To generatethe first message, the UE may generate the preamble and may generate atleast one reference signal for the payload. The first message may beassociated with one or more uplink data channel (e.g., PUSCH) occasionsand one or more reference signals (e.g., DMRSs), and thus, the UE maymultiplex data on the one or more uplink data channel occasions and theat one or more reference signals for the payload. In some aspects, theUE may further multiplex and/or otherwise piggyback UCI with the data onthe one or more uplink data channel occasions and the one or more DMRSsfor the payload. For example, referring to FIG. 4, the UE 404 maygenerate the msgA 414 associated with the two-step RACH procedure 410,and the UE 404 may generate the msgA 414 to include the preamble 422 andthe payload 426.

The UE may determine an MCS to be applied to the payload. In someaspects, at least one of the MCS configured for the payload and/or thesize of the payload may be associated with the RRC state of the UE. Insome other aspects, the UE may generate the preamble of the firstmessage to indicate at least one of the MCS configured for the payloadand/or the size of the payload. In some further aspects, the UE maygenerate the preamble based on a sequence, and at least one of thelength of the sequence and/or an SCS configured for the preamble may bebased on at least one of the type of cell operated by the base stationand/or the RRC state of the UE.

At operation 806, the UE may determine at least one power control schemeto be used for transmission of the first message. In some aspects, theUE may determine the at least one power control scheme based on the MCSconfigured for the payload. In some other aspects, the UE may determinethe at least one power control scheme based on a bandwidth configuredfor the payload. For example, the UE may determine at least twodifferent power control schemes indicated by the received configurationinformation, and the UE may select one power control scheme for thepreamble. Further, the UE may select another power control scheme basedon the MCS configured for the payload and/or based on the bandwidthconfigured for the payload, such as by identifying an MCS-dependentand/or bandwidth-dependent power control scheme indicated in thereceived configuration information that corresponds with the MCS and/orbandwidth, respectively, configured for the payload.

According to various aspects, the UE may determine two different powercontrol schemes for transmission of the first message: a first powercontrol scheme for transmission of the preamble of the first message anda second power control scheme for transmission of the payload of thefirst message. The first power control scheme may include an initialtransmission power and a power ramping step for retransmissions, whereasthe second power control scheme may be determined based on the MCSand/or bandwidth configured for the payload. The UE may determine thetwo different power control schemes based on the received configurationinformation, which may indicate at least two different power controlschemes associated with transmission of the first message for the RACHprocedure.

For example, referring to FIG. 4, the UE 404 may determine at least onepower control scheme to be used for transmission of the payload 426 ofthe msgA 414 based on the MCS and/or bandwidth configured for thepayload 426. The UE 404 may determine the at least one power controlscheme based on the received configuration information 420, which mayindicate at least two different power control schemes.

At operation 808, the UE may transmit the first message to the basestation using at least one of the at least two different RACH requestconfiguration parameters. The at least one of the at least two differentRACH request configuration parameters may correspond to an RRC state ofthe UE. For example, the UE may transmit the first message to the basestation using the determined power control scheme of the at least twodifferent power control schemes, which may correspond to the RRC stateof the UE. The UE may transmit the first message to the base station toinitiate a two-step RACH procedure with the base station. The UE maytransmit the preamble of the first message using the aforementionedfirst power control scheme, and may transmit the payload of the firstmessage using the aforementioned second (MCS-dependent and/orbandwidth-dependent) power control scheme.

The UE may transmit the preamble of the first message on a first set ofresources associated with a RACH occasion, and may transmit the payloadof the first message on a second set of resources. According to variousaspects, the UE may transmit the preamble on a different bandwidthportion (or part) than the payload, via a different beam pair than thepayload, and/or with a different SCS than the payload.

In some aspects, the UE may transmit the preamble based on at least oneconfiguration for the first set of resources associated with the RACHoccasion in the time domain, the frequency domain, and/or the spatialdomain. For example, the UE may determine the first set of resourcesassociated with the RACH occasion based on one or more of the following,as indicated in the received configuration information: theconfiguration index (e.g., a PRACH configuration index) associated withthe at least one configuration in the time domain, the number of RACHoccasions available for the RACH procedure associated with the at leastone configuration in the frequency domain, the starting frequencyresource associated with the RACH occasions, the number of preamblesequences per SS/PBCH block, and/or the number of SS/PBCH blocksassociated with each of the RACH occasions.

Further, the UE 404 may insert a time gap between the preamble and thepayload when transmitting the first message. The time gap may be anumber of slots (including a fractional number), a number of symbols(including a fractional number), or may be zero. The duration (e.g.,number of slots or symbols) may be configurable by the base station forthe UE. For example, the configuration information received by the UEmay indicate the duration of the time gap.

For example, referring to FIG. 4, the UE 404 may transmit the msgA 414to the base station 402 using at least one power control scheme of atleast two different power control schemes configured by the base station402 for the UE 404 (e.g., via the configuration information 420). The UE404 may transmit the preamble 422 on a first set of resources associatedwith the RACH occasion 412, and may transmit the payload 426 on a secondset of resources. In some aspect, the UE 404 may insert the gap 424between the preamble 422 and the payload 426 of the msgA 414, and theduration of the gap 424 may be configured by the base station 402 (e.g.,via the configuration information 420).

At operation 810, the UE may receive a second message associated withthe RACH procedure from the base station. The second message may includecontrol information on a downlink control channel (e.g., a PDCCH) anddata on a downlink data channel (e.g., PDSCH). The second message may bea msgB that is associated with contention resolution, fallback, and/ormsgA retransmission. Effectively, the second message (e.g., msgB) mayenable completion of the two-step RACH procedure initiated by the UEthrough transmission of the first message—e.g., the two-step RACHprocedure may be completed when the UE transmits an acknowledgement(ACK) message in response to the received msgB.

For example, referring to FIG. 4, the UE 404 may receive the msgB 416from the base station 402 to complete the two-step RACH procedure 410,which may be initiate by the msgA 414 transmitted by the UE 404 to thebase station 402. The msgB 416 may include control information on thedownlink control channel 432 (e.g., PDCCH) and data on the downlink datachannel 434 (e.g., PDSCH).

With reference to FIG. 9, a flowchart illustrates a method 900 ofwireless communication. The method 900 may be performed by a UE (e.g.,the UE 104, 350, 404; the apparatus 1202/1202′; the processing system1314, which may include the memory 360 and which may be the entire UE104, 350, 404 or a component of the UE 104, 350, 404, such as the TXprocessor 368, the RX processor 356, and/or the controller/processor359). One or more of the illustrated operations may be omitted,transposed, or contemporaneous. Various optional operations may beillustrated with dashed lines.

At operation 902, the UE may generate a payload of a first message. Thepayload may include at least one DMRS and data in a PUSCH. In oneaspect, a portion of the information in the PUSCH at least partiallyindicates an ID associated with the UE. For example, referring to FIG.4, the UE 404 may generate the payload 426 of the msgA 414, which mayinclude the at least one reference signal 428 and the uplink datachannel 430. Referring to FIG. 5, the UE may generate a payload 502 thatmay be configured for transmission in the TX chain 500 to comprise theuplink data channel/reference signal 530 of the msgA 524.

At operation 904, the UE may determine at least one of a cyclic shift orroot sequence index based on at least one of a size of the payloadand/or MCS associated with the first message. Referring to FIG. 4, theUE 404 may determine at least one of a cyclic shift or root sequenceindex for the preamble 422 based on at least one of a size of thepayload 526 and/or the MCS to be applied to the payload 526. Referringto FIG. 5, the UE may generate the preamble 522 based on at least one ofa size of the payload 502 and/or an MCS to be applied to the uplink datachannel/reference signal 530 of the payload 502. Referring to the thirdconfiguration 640 of FIG. 6, the UE may generate a preamble according toa sequence configuration for the first preamble set 602 in order toindicate a first MCS and first TB size, or the UE may generate apreamble according to a sequence configuration for the second preambleset 604 in order to indicate a second MCS and a second TB size.

At operation 906, the UE may determine a first set of resources fortransmission of the first message based on at least one of the size ofthe payload and/or the MCS associated with the first message. Referringto FIG. 4, the UE 404 may determine a first set of resources fortransmission of the preamble 422 of the msgA 414 based on at least oneof a size of the payload 426 and/or the MCS to be applied to the payload426 of the msgA 414. Referring to FIG. 5, the radio resource mapping 518may occur in the TX chain 500 for the preamble 522. Referring to thefirst configuration 600 of FIG. 6, the UE may transmit a preamble of thefirst preamble set 602 in a first set of symbols and a first set ofsubcarriers in order to indicate a first MCS and first TB size, and theUE may transmit a preamble of the second preamble set in at leastpartially the first set of symbols but in a second set of subcarriers toindicate a second MCS and a second TB size. Referring to the secondconfiguration 620 of FIG. 6, the UE may transmit a preamble of the firstpreamble set 602 in a first set of symbols and a first set ofsubcarriers in order to indicate a first MCS and first TB size, and theUE may transmit a preamble of the second preamble set in a second set ofsymbols but in at least partially the first set of subcarriers toindicate a second MCS and a second TB size.

At operation 908, the UE may determine at least one of a TB size or MCSassociated with the first message based on an RRC state of the UE.Referring to FIG. 4, the UE 404 may determine at least one of a TB sizefor the payload 426 or MCS associated with the payload 426 of the msgA414 based on an RRC state of the UE 404.

At operation 910, the UE may identify a preamble sequence index based onan ID associated with the UE. Referring to FIG. 4, the UE 404 mayidentify a preamble sequence index for generation of the preamble 422based on an ID associated with the UE 404.

At operation 912, the UE may identify a DMRS sequence index based on anID associated with the UE. In one aspect, the UE may generate thepayload based on the DMRS sequence identified based on the ID associatedwith the UE. Referring to FIG. 4, the UE 404 may identify a DMRSsequence index for generation of the at least one reference signal 428based on an ID associated with the UE 404.

At operation 914, the UE may scramble the payload using a code based onan ID associated with the UE. Referring to FIG. 4, the UE 404 mayscramble the payload 426 using a code based on an ID associated with theUE 404. Referring to FIG. 5, bit scrambling 506 may be applied to thepayload 502 in the TX chain 500 based on an ID associated with the UE404.

At operation 916, the UE may mask a CRC included in the first messagebased on an ID associated with the UE. Referring to FIG. 4, the UE 404may mask a CRC included in the msgA 414 based on an ID associated withthe UE 404. Referring to FIG. 5, the LDPC channel encoder 504 may mask aCRC included with the payload 502 in the TX chain 500 based on an IDassociated with the UE 404.

At operation 918, the UE may generate a preamble associated with a RACHprocedure. In one aspect, the UE may generate the preamble based on atleast one of a size of the payload or an MCS associated with the firstmessage. In one aspect, the UE may generate the preamble based on atleast one of the cyclic shift or the root index identified based on theat least one of the size of the payload or the MCS associated with thefirst message. In one aspect, the UE may generate the preamble based onthe preamble sequence index identified based on an ID associated withthe UE. Referring to FIG. 4, the UE may generate the preamble 422associated with the RACH procedure 410. Referring to FIG. 5, the UE maygenerate the preamble 522. Referring to FIG. 7, the UE may generate apreamble to include a set of concatenated sequences 702 a, 702 b, 702 m,which may be time-division multiplexed as illustrated in the firstconfiguration 700 or frequency-division/space-division multiplexed asillustrated in the second configuration 720.

At operation 920, the UE may transmit, in a first message to initiatethe RACH procedure with a base station, the preamble on a first set ofresources and the payload on a second set of resources. In some aspects,a gap in time may be included in the first message between the preambleand the payload. In one aspect, the second set of resources is based onat least one of a size of the cell provided by the base station or anRRC state of the UE. In one aspect, the preamble may be transmitted witha different transmission power than the payload. In one aspect, thepreamble occupies a different bandwidth portion than the payload. In oneaspect, the preamble is transmitted on a different beam than thepayload. In one aspect, the preamble is transmitted with a different SCSthan the payload. Referring to FIG. 4, the UE 404 may transmit, in themsgA 414 to initiate the RACH procedure 410 with the base station 402,the preamble 422 on a first set of resources and the payload 426 on asecond set of resources. Referring to FIG. 5, the radio resource mapping518 in the TX chain 500 may assign the preamble 522 to a first set ofresources and may assign the uplink data channel/reference signal 530 toa second set of resources, and the TX chain 500 may transmit the msgA524 including the preamble 522 and the uplink data channel/referencesignal 530.

FIG. 10 is a flowchart of a method 1000 for operation 918, at which athe UE generates a preamble associated with a RACH procedure. Atoperation 1002, the UE may generate a first preamble. Referring to FIG.4, the UE 404 may generate a first sequence for the preamble 422.Referring to FIG. 5, the UE may generate a first sequence for thepreamble 522. Referring to FIG. 7, the UE may generate a first sequence702 a of the sequences 702 a, 702 b, 702 m for transmission in thepreamble transmission occasion.

At operation 1004, the UE may generate at least one second preamble.Referring to FIG. 4, the UE 404 may generate at least one secondsequence for the preamble 422. Referring to FIG. 5, the UE may generateat least one second sequence for the preamble 522. Referring to FIG. 7,the UE may generate the second through m^(th) sequences 702 b, 702 m fortransmission in the preamble transmission occasion.

At operation 1006, the UE concatenate the first preamble and the atleast one second preamble. In various aspects, the first preamble andthe at least one second preamble may be one of time-divisionmultiplexed, frequency-division multiplexed, or space-divisionmultiplexed. Referring to FIG. 4, the UE 404 may concatenate the firstsequence and the at least one second sequence for the preamble 422.Referring to FIG. 5, the UE may concatenate the first sequence and theat least one second sequence for the preamble 522. Referring to thefirst configuration 700 of FIG. 7, the UE may concatenate the sequences702 a, 702 b, 702 m by time-division multiplexing the sequences 702 a,702 b, 702 m in different sets of symbols and sending the sequences 702a, 702 b, 702 m in a same set of subcarriers and/or on a same beam.Referring to the second configuration 720 of FIG. 7, the UE mayconcatenate the sequences 702 a, 702 b, 702 m by frequency-divisionmultiplexing in different sets of subcarriers and/or space-divisionmultiplexing the sequences 702 a, 702 b, 702 m on different beams andsending the sequences 702 a, 702 b, 702 m in a same set of symbols.

Referring now to FIG. 11, a flowchart shows a method 1100 of wirelesscommunication. The method 1100 may be performed by a base station (e.g.,the base station 102/180, 310, 402; the apparatus 1402/1402′; theprocessing system 1514, which may include the memory 376 and which maybe the entire base station 102/180, 310, 402 or a component of the basestation 102/180, 310, 402, such as the TX processor 316, the RXprocessor 370, and/or the controller/processor 375). One or more of theillustrated operations may be omitted, transposed, or contemporaneous.Various optional operations may be illustrated with dashed lines.

At operation 1102, the base station may transmit configurationinformation indicating at least two different RACH request configurationparameters associated with a RACH procedure. For example, the RACHprocedure may be a two-step RACH procedure, and the at least twodifferent RACH request configuration parameters may indicate at leasttwo different preamble groups, at least two different payload sizes, atleast two different MCSs, at least two different time and frequencyresource allocations, and/or or at least two different power controlschemes. Each of the at least two different RACH request configurationparameters may correspond to a respective RRC state in which a UE mayoperate, such as RRC Idle, RRC Inactive, or RRC Connected. The basestation may transmit the configuration in one or more messages, such asin at least one SIB and/or via RRC signaling to the UE. For example,referring to FIG. 4, the base station 402 may transmit the configurationinformation 420, which may include information associated with the RACHprocedure 410.

In some aspects, the configuration information may indicate at least twodifferent power control schemes associated with transmission of a firstmessage for a two-step RACH procedure. According to various aspects, theconfiguration information may further indicate at least oneconfiguration in the time domain, the frequency domain, and/or thespatial domain for a first set of resources associated with a RACHoccasion on which at least a portion of a first message for the RACHprocedure is to be transmitted. For example, the configurationinformation may indicate at least one of a configuration index (e.g., aPRACH configuration index) associated with the at least oneconfiguration in the time domain, a number of RACH occasions availablefor the RACH procedure associated with the at least one configuration inthe frequency domain, a starting frequency resource associated with theRACH occasions, a number of preamble sequences per SS/PBCH block, and/ora number of SS/PBCH blocks associated with each of the RACH occasions.

In some other aspects, the configuration information may indicate acorrespondence between each RRC state of a set of RRC states and atleast one of a TB size or an MCS associated with the first message.Additionally or alternatively, the configuration information mayindicate a correspondence one or more sequence configurations and atleast one of a type of cell operated by the base station and/or an RRCstate of a UE. For example, the configuration information may indicateat least one of a sequence length associated with a preamble of the RACHprocedure and/or SCS associated with the first message of the RACHprocedure corresponding with at last one of a type of cell operated bythe base station and/or an RRC state of a UE.

At operation 1104, the base station may receive a first messageassociated with the RACH procedure from a UE based on the configurationinformation. For example, the first message may be a msgA initiating atwo-step RACH procedure. A preamble of the first message may be receivedon a first set of resources associated with a RACH occasion and apayload of the first message may be received on a second set ofresources. The second set of resources may be used for the transmissionof msgA payload (e.g., DMRS and data carried on a PUSCH), which may bereferred to as “PUSCH occasion with associated DMRS signal.” The payloadmay include at least one reference signal (e.g., at least one DMRS) anddata on an uplink data channel (e.g., a PUSCH). For example, referringto FIG. 4, the base station 402 may receive, from the UE 404, the msgA414 associated with initiation of the RACH procedure 410. The basestation 402 may receive the preamble 422 of the msgA 414 on a first setof resources and may receive the payload 426 of the msgA 414 on a secondset of resources.

The first message may include a gap in time between the preamble and thepayload. The gap in time may be a number of slots (including fractionalnumbers), a number of symbols (including fractional numbers), or may bezero. The gap in time may be configured by the base station for the UE,e.g., via the transmitted configuration information.

In one aspect, the preamble may comprise a first preamble and at leastone second preamble concatenated with the first preamble, and the firstpreamble and the at least one second preamble may be time-divisionmultiplexed, frequency-division multiplexed, or space-divisionmultiplexed. In one aspect, the configuration information may indicatethe second set of resource in which the payload is located. In oneaspect, the preamble occupies a different bandwidth portion than thepayload, the preamble is received on a different beam than the payload,and/or the preamble is received with a different SCS than the payload.

At operation 1106, the base station may determine at least one of a sizeof the payload or an MCS configured for the payload based on thepreamble of the first message. Referring to FIG. 4, the base station 402may determine at least one of a size of the payload 426 and/or an MCSapplied to the payload 426 based on the preamble 422 of the msgA 414.

In some other aspects, the base station may determine the at least oneof the size of the payload or the MCS associated with the first messagebased on at least one of the first set of resources in which thepreamble is located or a sequence configuration of the preamble. In afurther aspect, at least one of the size of the payload and/or the MCSconfigured for the payload indicates an RRC state of the UE.Accordingly, the base station may determine the RRC state of the UEbased on at least one of the size of the payload and/or the MCSconfigured for the payload. In still another aspect, at least one of asequence length associated with the preamble and/or an SCS associatedwith receiving the first message is based on at least one of the type ofcell operated by the base station and/or the RRC state of the UE. Forexample, the base station may determine the RRC state of the UE based onat least one of a sequence length associated with the preamble and/or anSCS associated with receiving the first message.

At operation 1108, the base station may determine an ID associated withthe UE based on at least one of a preamble sequence index associatedwith the preamble, a DMRS sequence associated with at least onereference signal in the payload, a subset of a set of bits (e.g., databits on the uplink data channel) in the payload, a scrambling codeapplied to the payload, and/or a mask applied to a CRC included in thefirst message. Referring to FIG. 4, the base station 402 may determinean ID associated with the UE 404 based on at least one of a preamblesequence index associated with the preamble 422, a DMRS sequenceassociated with the at least one reference signal 428 in the payload426, a subset of a set of bits in the payload 426, a scrambling codeapplied to the payload 426, and/or a mask applied to a CRC included inthe msgA 414.

At operation 1110, the base station may transmit a second messageassociated with the RACH procedure to the UE in response to the firstmessage. For example, the second message may be a msgB that completesthe two-step RACH procedure. The second message may include controlinformation on a downlink control channel (e.g., a PDCCH) and data on adownlink data channel (e.g., a PDSCH). Referring to FIG. 4, the basestation 402 may send, to the UE 404 in response to the msgA 414, themsgB 416 associated with completion of the RACH procedure 410. The msgB416 may include control information on the downlink control channel 432and data on the downlink data channel 434.

FIG. 12 is a conceptual data flow diagram illustrating the data flow1200 between different means/components in an example apparatus 1202.The apparatus 1202 may be a UE. The apparatus 1202 may include areception component 1204 configured to receive configuration informationfrom a base station 1250 that indicates at least two different powercontrol schemes, e.g., as described in connection with operation 802 ofFIG. 8. The configuration information may be included in at least one ofa SIB and/or an RRC message from the base station 1250.

In some aspects, the configuration information may indicate at least oneconfiguration in the time domain, frequency domain, and/or spatialdomain for a first set of resources associated with a RACH occasion onwhich a msgA may be transmitted to the base station 1250. For example,the configuration information may indicate at least one of aconfiguration index (e.g., a PRACH configuration index) associated withthe at least one configuration in the time domain, a number of RACHoccasions available for a RACH procedure associated with the at leastone configuration in the frequency domain, a starting frequency resourceassociated with the RACH occasions, a number of preamble sequences perSS/PBCH block, and/or a number of SS/PBCH blocks associated with each ofthe RACH occasions.

The apparatus 1202 may further include a message generation component1208 configured to generate a first message associated with a RACHprocedure, e.g., as described in connection with operation 804 of FIG.8. The first message may be a msgA of a two-step RACH procedure, and mayinclude a preamble and a payload. The payload may include data on anuplink data channel and at least one reference signal. In some aspects,the uplink data channel may be a PUSCH, and the at least one referencesignal may be a DMRS.

In some aspects, the message generation component 1208 may generate thepreamble to indicate at least one of a size of the payload or an MCSconfigured for the payload. In some other aspects, an RRC state of theapparatus 1202 may be associated with at least one of the size of thepayload or the MCS configured for the payload. In some further aspects,at least one of a sequence length associated with the preamble or an SCSassociated with the first message may be based on at least one of a typeof cell operated by the base station 1250 and/or the RRC state of theapparatus 1202.

The message generation component 1208 may generate the first message toinclude a time gap between the preamble and the payload of the firstmessage. The time gap may be a number of slots and/or symbols, includingfractional numbers. Potentially, the time gap may be zero. The basestation 1250 may configure the time gap for the message generationcomponent 1208, such as via RRC signaling.

The apparatus 1202 may further include a RACH configuration component1210 configured to determine at least one power control schemeassociated with transmission of the first message, e.g., as described inconnection with operation 806 of FIG. 8. The RACH configurationcomponent 1210 may determine the at least one power control scheme basedon at least two different power control schemes indicated in thereceived configuration information.

The RACH configuration component 1210 may determine the at least onepower control scheme based on the MCS configured for the payload. Insome aspects, the RACH configuration component 1210 may determine twodifferent power control schemes for transmission of the first message:one power control scheme for transmission of the preamble of the firstmessage, and another power control scheme (e.g., an MCS-dependent powercontrol scheme) for transmission of the payload of the first message.

The RACH configuration component 1210 may assign the preamble to a firstset of resources associated with a RACH occasion, and may assign thepayload to a second set of resources. For example, the preamble may beassigned to occupy a different bandwidth portion (e.g., bandwidth part)than the payload. In some aspects, the RACH configuration component 1210may assign the preamble for transmission via a different beam pair thanthe payload. In some other aspects, the RACH configuration component1210 may configure the preamble with a different SCS than the payload.

The RACH configuration component 1210 may determine the RACH occasionassociated with the first set of resources to which the preamble isassigned based on the indication in the received configurationinformation of at least one configuration in the time domain, frequencydomain, and/or spatial domain. For example, the RACH configurationcomponent 1210 may determine the RACH occasion based on at least one ofthe configuration index (e.g., a PRACH configuration index) associatedwith the at least one configuration in the time domain, the number ofRACH occasions available for a RACH procedure associated with the atleast one configuration in the frequency domain, the starting frequencyresource associated with the RACH occasions, the number of preamblesequences per SS/PBCH block, and/or the number of SS/PBCH blocksassociated with each of the RACH occasions.

The apparatus 1202 may further include a transmission component 1206configured to transmit the first message to the base station 1250 usingthe at least one power control scheme (determined by the RACHconfiguration component 1210) of the at least two different powercontrol schemes configured by the base station 1250 (e.g., via thereceived configuration information), e.g., as described in connectionwith operation 808 of FIG. 8. For example, the first message may be amsgA that initiates a two-step RACH procedure. The transmissioncomponent 1206 may transmit the preamble on the first set of resourcesassociated with the RACH occasion, and may transmit the payload on thesecond set of resources, as configured by the RACH configurationcomponent 1210.

The transmission component 1206 may transmit the preamble according to adifferent one of the at least two power control schemes configured bythe base station 1250 than that of the payload (e.g., the payload may betransmitted with an MCS-dependent power control scheme, whereas thepower control scheme according to which the preamble is transmitted maynot be MCS-dependent).

The reception component 1204 of the apparatus 1202 may be furtherconfigured to receive a second message associated with the RACHprocedure from the base station 1250, e.g., as described in connectionwith operation 810 of FIG. 8. For example, the second message may be amsgB that completes the two-step RACH procedure. The second message mayinclude control information on a downlink control channel (e.g., aPDCCH) and data on a downlink data channel (e.g., a PDSCH).

The apparatus 1202 may include additional components that perform eachof the blocks of the algorithm in the aforementioned flowcharts of FIGS.8-10. As such, each block in the aforementioned flowcharts of FIGS. 8-10may be performed by a component and the apparatus 1202 may include oneor more of those components. The components may be one or more hardwarecomponents specifically configured to carry out the statedprocesses/algorithm, implemented by a processor configured to performthe stated processes/algorithm, stored within a computer-readable mediumfor implementation by a processor, or some combination thereof.

FIG. 13 is a diagram illustrating an example of a hardwareimplementation 1300 for an apparatus 1202′ employing a processing system1314. The processing system 13114 may be implemented with a busarchitecture, represented generally by the bus 1324. The bus 1324 mayinclude any number of interconnecting buses and bridges depending on thespecific application of the processing system 1314 and the overalldesign constraints. The bus 1324 links together various circuitsincluding one or more processors and/or hardware components, representedby the processor 1304, the components 1204, 1206, 1208, 1210 and thecomputer-readable medium/memory 1306. The bus 1324 may also link variousother circuits such as timing sources, peripherals, voltage regulators,and power management circuits, which are well known in the art, andtherefore, will not be described any further.

The processing system 1314 may be coupled to a transceiver 1310. Thetransceiver 1310 is coupled to one or more antennas 1320. Thetransceiver 1310 provides a means for communicating with various otherapparatus over a transmission medium. The transceiver 1310 receives asignal from the one or more antennas 1320, extracts information from thereceived signal, and provides the extracted information to theprocessing system 1314, specifically the reception component 1204. Inaddition, the transceiver 1310 receives information from the processingsystem 1314, specifically the transmission component 1206, and based onthe received information, generates a signal to be applied to the one ormore antennas 1320. The processing system 1314 includes a processor 1304coupled to a computer-readable medium/memory 1306. The processor 1304 isresponsible for general processing, including the execution of softwarestored on the computer-readable medium/memory 1306. The software, whenexecuted by the processor 1304, causes the processing system 1314 toperform the various functions described supra for any particularapparatus. The computer-readable medium/memory 1306 may also be used forstoring data that is manipulated by the processor 1304 when executingsoftware. The processing system 1314 further includes at least one ofthe components 1204, 1206, 1208, 1210. The components may be softwarecomponents running in the processor 1304, resident/stored in thecomputer readable medium/memory 1306, one or more hardware componentscoupled to the processor 1304, or some combination thereof. Theprocessing system 1314 may be a component of the UE 350 and may includethe memory 360 and/or at least one of the TX processor 368, the RXprocessor 356, and the controller/processor 359. Alternatively, theprocessing system 1314 may be the entire UE (e.g., see 350 of FIG. 3).

In one configuration, the apparatus 1202/1202′ for wirelesscommunication includes means for receiving configuration informationfrom a base station, the configuration information indicating at leasttwo different random access channel (RACH) request configurationparameters that each is associated with a respective radio resourcecontrol (RRC) state; means for generating a first message associatedwith a two-step RACH procedure including a preamble and a payload, thepayload including data on an uplink data channel and at least onereference signal; and means for transmitting the first message to thebase station using at least one of the at least two different RACHrequest configuration parameters that corresponds to an RRC state of theUE, the preamble being transmitted on a first set of resourcesassociated with a RACH occasion and the payload being transmitted on asecond set of resources.

In one aspect, the uplink data channel includes a PUSCH, and the atleast one reference signal includes a DMRS. In one aspect, theconfiguration information is included in at least one of a SIB or a RRCmessage from the base station. The apparatus 1202/1202′ may furtherinclude means for determining at least one power control scheme fortransmission of the first message based on a MCS and bandwidthconfigured for the payload, and the at least one power control schememay be included in the at least two different RACH request configurationparameters.

In one aspect, the preamble and the payload are transmitted usingdifferent ones of the at least two different RACH request configurationparameters. In one aspect, the first message comprises a time gapbetween the preamble and the payload, and the time gap comprises aconfigurable number of slots or symbols between the preamble and thepayload. In one aspect, the preamble indicates at least one of a size ofthe payload or a MCS configured for the payload. In one aspect, theconfiguration information indicates at least one configuration in a timedomain, a frequency domain, or a spatial domain for the first set ofresources associated with the RACH occasion. The configurationinformation may indicate at least one of: a PRACH configuration indexassociated with at least one RACH occasion configuration in the timedomain, a number of RACH occasions available for the RACH procedureassociated with the at least one configuration in the frequency domain,a starting frequency resource associated with the RACH occasions, anumber of preamble sequences per SS/PBCH block, or a number of SS/PBCHblocks associated with each of the RACH occasions.

In one aspect, the RRC state of the UE is associated with at least oneof a size of the payload or a MCS configured for the payload. In oneaspect, at least one of a sequence length associated with the preambleor a subcarrier spacing associated with the transmitting the firstmessage is based on at least one of a type of a cell operated by thebase station or the RRC state of the UE. In one aspect, the preambleoccupies a different bandwidth portion than the payload, the preamble istransmitted with a different target power or a different power rampingstep size than the payload, the preamble is transmitted via a differentbeam pair than the payload, or the preamble is transmitted with adifferent subcarrier spacing than the payload.

In one aspect, the apparatus 1202/1202′ may further include means forreceiving a second message associated with the two-step RACH procedurefrom the base station in response to the first message, wherein thesecond message includes control information on a downlink controlchannel and data on a downlink data channel. In one aspect, the firstmessage comprises a msgA initiating the two-step RACH procedure and thesecond message comprises a msgB enabling completion of the two-step RACHprocedure.

The aforementioned means may be one or more of the aforementionedcomponents of the apparatus 1202 and/or the processing system 1314 ofthe apparatus 1202′ configured to perform the functions recited by theaforementioned means. As described supra, the processing system 1314 mayinclude the TX Processor 368, the RX Processor 356, and thecontroller/processor 359. As such, in one configuration, theaforementioned means may be the TX Processor 368, the RX Processor 356,and the controller/processor 359 configured to perform the functionsrecited by the aforementioned means.

FIG. 14 is a conceptual data flow diagram illustrating the data flow1400 between different means/components in an example apparatus 1402.The apparatus 1402 may be a base station. The apparatus 1402 includes aRACH configuration component 1408 configured to determine configurationinformation associated with a RACH procedure (e.g., a two-step RACHprocedure). The RACH configuration component 1408 may include at leasttwo different power control schemes associated with transmission of afirst message (e.g., a msgA) initiating the RACH procedure.

In some aspects, the RACH configuration component 1408 may include, inthe configuration information, at least one configuration in the timedomain, the frequency domain, and/or the spatial domain for a first setof resources associated with a RACH occasion. For example, theconfiguration information may indicate at least one of a configurationindex (e.g., a PRACH configuration index) associated with the at leastone configuration in the time domain, a number of RACH occasionsavailable for the RACH procedure associated with the at least oneconfiguration in the frequency domain, a starting frequency resourceassociated with the RACH occasions, a number of preamble sequences perSS/PBCH block, and/or a number of SS/PBCH blocks associated with each ofthe RACH occasions.

The apparatus 1402 may further include a transmission component 1406configured to transmit the configuration information indicating at leasttwo different power control schemes associated with the RACH procedure,e.g., as described in connection with operation 1102 of FIG. 11. Forexample, the transmission component 1406 may transmit the configurationinformation in at least one RRC message to the UE and/or may broadcastthe configuration information in at least one SIB.

The apparatus 1402 may further include a reception component 1404configured to receive a first message associated with the RACHprocedure, e.g., as described in connection with operation 1104 of FIG.11. For example, the first message may be a msgA initiating the(two-step) RACH procedure. According to various aspects, the preamblemay occupy a different bandwidth portion of the payload, the preamblemay be received via a different beam pair than the payload, and/or thepreamble may be received with a different SCS than the payload.

The first message may include a time gap between the preamble and thepayload. The time gap may be a configurable number of slots and/orsymbols (e.g., including fractional numbers) between the preamble andthe payload. For example, the time gap may be configured by the UE 1450based on the configuration information.

The apparatus 1402 may include a RACH messaging component 1410configured to determine at least one of a size of the payload or an MCSconfigured for the payload based on the preamble of the first message,e.g., as described in connection with operation 1106 of FIG. 11. In someaspects, at least one of the size of the payload and/or the MCSconfigured for the payload may indicate an RRC state of the UE 1450.

In some other aspects, at least one of a sequence length associated withthe preamble and/or the SCS configured for the first message (e.g.,configured for the preamble) may be based on at least one of a type ofcell operated by the apparatus 1402 and/or the RRC state of the UE 1450.

In some aspects, the RACH messaging component 1410 may be furtherconfigured to determine an ID associated with the UE 1450 based on atleast one of a preamble sequence index associated with the preamble, aDMRS sequence associated with at least one reference signal in thepayload, a subset of a set of bits (e.g., data bits on the uplink datachannel) in the payload, a scrambling code applied to the payload,and/or a mask applied to a CRC included in the first message, e.g., asdescribed in connection with operation 1108 of FIG. 11.

The RACH messaging component 1410 may be further configured to generatea second message associated with the RACH procedure. The second messagemay be a msgB that completes the (two-step) RACH procedure. The RACHmessaging component 1410 may generate the second message to includecontrol information on a downlink control channel (e.g., a PDCCH) anddata on a downlink data channel (e.g., a PDSCH).

The transmission component 1406 may be further configured to transmitthe second message associated with the RACH procedure to the UE 1450 inresponse to receiving the first message, e.g., as described inconnection with operation 1110 of FIG. 11. The transmission component1406 may transmit the control information on the downlink data channel(e.g., the PDCCH) and transmit the data on the downlink data channel(e.g., the PDSCH).

The apparatus 1402 may include additional components that perform eachof the blocks of the algorithm in the aforementioned flowchart of FIG.11. As such, each block in the aforementioned flowchart of FIG. 11 maybe performed by a component and the apparatus 1402 may include one ormore of those components. The components may be one or more hardwarecomponents specifically configured to carry out the statedprocesses/algorithm, implemented by a processor configured to performthe stated processes/algorithm, stored within a computer-readable mediumfor implementation by a processor, or some combination thereof.

FIG. 15 is a diagram illustrating an example of a hardwareimplementation 1500 for an apparatus 1402′ employing a processing system1514. The processing system 1514 may be implemented with a busarchitecture, represented generally by the bus 1524. The bus 1524 mayinclude any number of interconnecting buses and bridges depending on thespecific application of the processing system 1514 and the overalldesign constraints. The bus 1524 links together various circuitsincluding one or more processors and/or hardware components, representedby the processor 1504, the components 1404, 1406, 1408, 1410 and thecomputer-readable medium/memory 1506. The bus 1524 may also link variousother circuits such as timing sources, peripherals, voltage regulators,and power management circuits, which are well known in the art, andtherefore, will not be described any further.

The processing system 1514 may be coupled to a transceiver 1510. Thetransceiver 1510 is coupled to one or more antennas 1520. Thetransceiver 1510 provides a means for communicating with various otherapparatus over a transmission medium. The transceiver 1510 receives asignal from the one or more antennas 1520, extracts information from thereceived signal, and provides the extracted information to theprocessing system 1514, specifically the reception component 1404. Inaddition, the transceiver 1510 receives information from the processingsystem 1514, specifically the transmission component 1406, and based onthe received information, generates a signal to be applied to the one ormore antennas 1520. The processing system 1514 includes a processor 1504coupled to a computer-readable medium/memory 1506. The processor 1504 isresponsible for general processing, including the execution of softwarestored on the computer-readable medium/memory 1506. The software, whenexecuted by the processor 1504, causes the processing system 1514 toperform the various functions described supra for any particularapparatus. The computer-readable medium/memory 1506 may also be used forstoring data that is manipulated by the processor 1504 when executingsoftware. The processing system 1514 further includes at least one ofthe components 1404, 1406, 1408, 1410. The components may be softwarecomponents running in the processor 1504, resident/stored in thecomputer readable medium/memory 1506, one or more hardware componentscoupled to the processor 1504, or some combination thereof. Theprocessing system 1514 may be a component of the base station 310 andmay include the memory 376 and/or at least one of the TX processor 316,the RX processor 370, and the controller/processor 375. Alternatively,the processing system 1514 may be the entire base station (e.g., see 310of FIG. 3).

In one configuration, the apparatus 1402/1402′ for wirelesscommunication includes means for transmitting configuration informationindicating at least two different RACH request configuration parametersthat each is associated with a respective RRC state; means for receivinga first message associated with the RACH procedure from a UE based onthe configuration information, a preamble of the first message beingreceived on a first set of resources associated with a RACH occasion anda payload of the first message being received on a second set ofresources; and means for transmitting a second message associated withthe RACH procedure to the UE in response to the first message, thesecond message including control information on a downlink controlchannel and data on a downlink data channel.

In one aspect, the downlink control channel includes a PDCCH and thedownlink data channel includes a PDSCH. In one aspect, the configurationinformation indicating the RACH request configuration parameters istransmitted in a RRC message to the UE or broadcast in a SIB. In oneaspect, the first message comprises a time gap between the preamble andthe payload, and the time gap comprises a configurable number of slotsor symbols between the preamble and the payload. In one aspect, theapparatus 1402/1402′ may further includes means for determining at leastone of a size of the payload or a MCS configured for the payload basedon the preamble of the first message. In one aspect, the configurationinformation indicates at least one configuration in a time domain, afrequency domain, or a spatial domain for the first set of resourcesassociated with the RACH occasion. In one aspect, the configurationinformation indicates at least one of: a configuration index associatedwith the configuration in the time domain, a number of RACH occasionsavailable for the RACH procedure associated with the configuration inthe frequency domain, a starting frequency resource associated with theRACH occasions, a number of preamble sequences per SS/PBCH block, or anumber of SS/PBCH blocks associated with each of the RACH occasions.

In one aspect, at least one of a size of the payload or a MCS configuredfor the payload is based on an RRC state of the UE. In one aspect, atleast one of a sequence length associated with the preamble or asubcarrier spacing associated with the receiving the first message isbased on at least one of a type of a cell operated by the base stationor an RRC state of the UE. In one aspect, the preamble occupies adifferent bandwidth portion than the payload, the preamble istransmitted with a different target power or a different power rampingstep size than the payload, the preamble is received via a differentbeam pair than the payload, or the preamble is received with a differentsubcarrier spacing than the payload. In one aspect, the RACH procedureincludes a two-step RACH procedure, and the first message includes amsgA initiating the two-step RACH procedure and the second messageincludes a msgB enabling completion of the two-step RACH procedure.

The aforementioned means may be one or more of the aforementionedcomponents of the apparatus 1402 and/or the processing system 1514 ofthe apparatus 1402′ configured to perform the functions recited by theaforementioned means. As described supra, the processing system 1514 mayinclude the TX Processor 316, the RX Processor 370, and thecontroller/processor 375. As such, in one configuration, theaforementioned means may be the TX Processor 316, the RX Processor 370,and the controller/processor 375 configured to perform the functionsrecited by the aforementioned means.

It is understood that the specific order or hierarchy of blocks in theprocesses/flowcharts disclosed is an illustration of example approaches.Based upon design preferences, it is understood that the specific orderor hierarchy of blocks in the processes/flowcharts may be rearranged.Further, some blocks may be combined or omitted. The accompanying methodclaims present elements of the various blocks in a sample order, and arenot meant to be limited to the specific order or hierarchy presented.

The previous description is provided to enable any person skilled in theart to practice the various aspects described herein. Variousmodifications to these aspects will be readily apparent to those skilledin the art, and the generic principles defined herein may be applied toother aspects. Thus, the claims are not intended to be limited to theaspects shown herein, but is to be accorded the full scope consistentwith the language claims, wherein reference to an element in thesingular is not intended to mean “one and only one” unless specificallyso stated, but rather “one or more.” The word “exemplary” is used hereinto mean “serving as an example, instance, or illustration.” Any aspectdescribed herein as “exemplary” is not necessarily to be construed aspreferred or advantageous over other aspects. Unless specifically statedotherwise, the term “some” refers to one or more. Combinations such as“at least one of A, B, or C,” “one or more of A, B, or C,” “at least oneof A, B, and C,” “one or more of A, B, and C,” and “A, B, C, or anycombination thereof” include any combination of A, B, and/or C, and mayinclude multiples of A, multiples of B, or multiples of C. Specifically,combinations such as “at least one of A, B, or C,” “one or more of A, B,or C,” “at least one of A, B, and C,” “one or more of A, B, and C,” and“A, B, C, or any combination thereof” may be A only, B only, C only, Aand B, A and C, B and C, or A and B and C, where any such combinationsmay contain one or more member or members of A, B, or C. All structuraland functional equivalents to the elements of the various aspectsdescribed throughout this disclosure that are known or later come to beknown to those of ordinary skill in the art are expressly incorporatedherein by reference and are intended to be encompassed by the claims.Moreover, nothing disclosed herein is intended to be dedicated to thepublic regardless of whether such disclosure is explicitly recited inthe claims. The words “module,” “mechanism,” “element,” “device,” andthe like may not be a substitute for the word “means.” As such, no claimelement is to be construed as a means plus function unless the elementis expressly recited using the phrase “means for.”

What is claimed is:
 1. A method of wireless communication by a userequipment (UE), the method comprising: receiving configurationinformation from a base station, the configuration informationindicating at least two different random access channel (RACH) requestconfiguration parameters that each is associated with a respective radioresource control (RRC) state; generating a first message associated witha two-step RACH procedure including a preamble and a payload, thepayload including data on an uplink data channel and at least onereference signal; and transmitting the first message to the base stationusing at least one of the at least two different RACH requestconfiguration parameters that corresponds to an RRC state of the UE, thepreamble being transmitted on a first set of resources associated with aRACH occasion and the payload being transmitted on a second set ofresources.
 2. The method of claim 1, wherein the uplink data channelcomprises a physical uplink shared channel (PUSCH), and the at least onereference signal comprises a demodulation reference signal (DMRS). 3.The method of claim 1, wherein the configuration information is includedin at least one of a system information block (SIB) or a RRC messagefrom the base station.
 4. The method of claim 1, further comprising:determining at least one power control scheme for transmission of thefirst message based on a modulation and coding scheme (MCS) andbandwidth configured for the payload, wherein the at least one powercontrol scheme is indicated in the at least two different RACH requestconfiguration parameters.
 5. The method of claim 1, wherein the preambleand the payload are transmitted using different power control schemesindicated by the at least one of the at least two different RACH requestconfiguration parameters.
 6. The method of claim 1, wherein the firstmessage comprises a time gap between the preamble and the payload, andthe time gap comprises a configurable number of slots or symbols betweenthe preamble and the payload.
 7. The method of claim 1, wherein thepreamble indicates at least one of a size of the payload or a modulationand coding scheme (MCS) configured for the payload.
 8. The method ofclaim 1, wherein the configuration information indicates at least oneconfiguration in a time domain, a frequency domain, or a spatial domainfor the first set of resources associated with the RACH occasion.
 9. Themethod of claim 8, where the configuration information indicates atleast one of: a physical RACH (PRACH) configuration index associatedwith at least one RACH occasion configuration in the time domain, anumber of RACH occasions available for the two-step RACH procedureassociated with the at least one configuration in the frequency domain,a starting frequency resource associated with the RACH occasions, anumber of preamble sequences per synchronization signal (SS)/physicalbroadcast channel (PBCH) block, or a number of SS/PBCH blocks associatedwith each of the RACH occasions.
 10. The method of claim 1, wherein theRRC state of the UE is associated with at least one of a size of thepayload or a modulation and coding scheme (MCS) configured for thepayload.
 11. The method of claim 1, wherein at least one of a sequencelength associated with the preamble or a subcarrier spacing associatedwith the transmitting the first message is based on at least one of atype of a cell operated by the base station or the RRC state of the UE.12. The method of claim 1, wherein: the preamble occupies a differentbandwidth portion than the payload, the preamble is transmitted with adifferent target power or a different power ramping step size than thepayload, the preamble is transmitted via a different beam pair than thepayload, or the preamble is transmitted with a different subcarrierspacing than the payload.
 13. The method of claim 1, further comprising:receiving a second message associated with the two-step RACH procedurefrom the base station in response to the first message, wherein thesecond message includes control information on a downlink controlchannel and data on a downlink data channel.
 14. The method of claim 13,wherein the first message comprises a msgA initiating the two-step RACHprocedure and the second message comprises a msgB enabling completion ofthe two-step RACH procedure.
 15. An apparatus for wireless communicationby a user equipment (UE), the apparatus comprising: a memory; and atleast one processor coupled to the memory and configured to: receiveconfiguration information from a base station, the configurationinformation indicating at least two different random access channel(RACH) request configuration parameters that each is associated with arespective radio resource control (RRC) state; generate a first messageassociated with a two-step RACH procedure including a preamble and apayload, the payload including data on an uplink data channel and atleast one reference signal; and transmit the first message to the basestation using at least one of the at least two different RACH requestconfiguration parameters that corresponds to an RRC state of the UE, thepreamble being transmitted on a first set of resources associated with aRACH occasion and the payload being transmitted on a second set ofresources.
 16. The apparatus of claim 15, wherein the uplink datachannel comprises a physical uplink shared channel (PUSCH), and the atleast one reference signal comprises a demodulation reference signal(DMRS).
 17. The apparatus of claim 15, wherein the configurationinformation is included in at least one of a system information block(SIB) or a radio resource control (RRC) message from the base station.18. The apparatus of claim 15, wherein the at least one processor isfurther configured to: determine at least one power control scheme fortransmission of the first message based on a modulation and codingscheme (MCS) and bandwidth configured for the payload, wherein the atleast one power control scheme is indicated in the at least twodifferent RACH request configuration parameters.
 19. The apparatus ofclaim 15, wherein the preamble and the payload are transmitted usingdifferent power control schemes indicated by the at least one of the atleast two different RACH request configuration parameters.
 20. Theapparatus of claim 15, wherein the first message comprises a time gapbetween the preamble and the payload, and the time gap comprises aconfigurable number of slots or symbols between the preamble and thepayload.
 21. The apparatus of claim 15, wherein the preamble indicatesat least one of a size of the payload or a modulation and coding scheme(MCS) configured for the payload.
 22. The apparatus of claim 15, whereinthe configuration information indicates at least one configuration in atime domain, a frequency domain, or a spatial domain for the first setof resources associated with the RACH occasion.
 23. The apparatus ofclaim 22, where the configuration information indicates at least one of:a physical RACH (PRACH) configuration index associated with at least oneRACH occasion configuration in the time domain, a number of RACHoccasions available for the two-step RACH procedure associated with theat least one configuration in the frequency domain, a starting frequencyresource associated with the RACH occasions, a number of preamblesequences per synchronization signal (SS)/physical broadcast channel(PBCH) block, or a number of SS/PBCH blocks associated with each of theRACH occasions.
 24. The apparatus of claim 15, wherein the RRC state ofthe UE is associated with at least one of a size of the payload or amodulation and coding scheme (MCS) configured for the payload.
 25. Theapparatus of claim 15, wherein at least one of a sequence lengthassociated with the preamble or a subcarrier spacing associated with thetransmitted first message is based on at least one of a type of a celloperated by the base station or the RRC state of the UE.
 26. Anapparatus for wireless communication by a user equipment (UE), theapparatus comprising: means for receiving configuration information froma base station, the configuration information indicating at least twodifferent random access channel (RACH) request configuration parametersthat each is associated with a respective radio resource control (RRC)state; means for generating a first message associated with a two-stepRACH procedure including a preamble and a payload, the payload includingdata on an uplink data channel and at least one reference signal; andmeans for transmitting the first message to the base station using atleast one of the at least two different RACH request configurationparameters that corresponds to an RRC state of the UE, the preamblebeing transmitted on a first set of resources associated with a RACHoccasion and the payload being transmitted on a second set of resources.27. The apparatus of claim 26, wherein the uplink data channel comprisesa physical uplink shared channel (PUSCH), and the at least one referencesignal comprises a demodulation reference signal (DMRS).
 28. Theapparatus of claim 26, wherein the configuration information is includedin at least one of a system information block (SIB) or a radio resourcecontrol (RRC) message from the base station.
 29. The apparatus of claim26, further comprising: means for determining at least one power controlscheme for transmission of the first message based on a modulation andcoding scheme (MCS) and bandwidth configured for the payload, whereinthe at least one power control scheme is indicated in the at least twodifferent RACH request configuration parameters.
 30. A computer-readablemedium storing computer executable code for wireless communication by auser equipment (UE), the code when executed by a processor cause theprocessor to: receive configuration information from a base station, theconfiguration information indicating at least two different randomaccess channel (RACH) request configuration parameters that each isassociated with a respective radio resource control (RRC) state;generate a first message associated with a two-step RACH procedureincluding a preamble and a payload, the payload including data on anuplink data channel and at least one reference signal; and transmit thefirst message to the base station using at least one of the at least twodifferent RACH request configuration parameters that corresponds to anRRC state of the UE, the preamble being transmitted on a first set ofresources associated with a RACH occasion and the payload beingtransmitted on a second set of resources.